Session 4A: V: On-Demand Poster Session - Available throughout DAMOP Meeting

Investigating ladder-type electromagnetically induced transparency in cesium

A ladder-type electromagnetically induced transparency (EIT) is investigated in room temperature cesium gas using two external-cavity diode lasers (ECDL). A weak probe laser at 852.3 nm was scanned across the 6S_1/2 → 6P_3/2 transition while a strong coupling beam at 520.3 nm was kept at resonance with the 6P_3/2 → 18D_5/2 transition to observe EIT features in Doppler broadened absorption spectra. Results are compared with the theoretical predictions.   

Photoionization of thiophene and 2-methylthiophene in the S 2p edge: influence of the methyl radical substitution in the fragmentation channels

Thiophene (C4H4S) is the simplest aromatic structure bearing sulfur, derived from benzene by the replacement of two CH groups by sulfur. Previous synchrotron-based studies probed thiophene photoionization by C 1s and S 2p photoelectron spectroscopy (Giertz et al.,2002), electron resolved PEPIPICO in the S 2p edge (Kukk et al., 2015) and core-hole clock spectroscopy in the S K-edge (Martins, 2021), whereas the molecular dynamics were investigated by FEL (Kukk, 2021). Methylthiophenes are formed by the replacement of a hydrogen atom in the thiophene by the methyl group. In contrast to the highly studied thiophene, methylthiophenes lack experimental data on their photoionization processes, with most of the spectroscopic studies on them focusing on their polymers (Rocco, 2004; Santa Rita, 2011). Thiophene, 2-methylthiophene, 3-methylthiophene and presumably benzothiophene were detected on Martian soil (Eigenbrode et al., 2018) through EGA and CG-MS onboard the Curiosity rover, along with 3-methylthiophene and presumably benzothiophene. Their discovery raised the question of its origin, whether biotic or abiotic (Heinz, 2020).

We have compared the stability and the photofragmentation pattern of thiophene and 2-methylthiophene upon photoionization. Photons from the Pleiades beamline at the French synchrotron facility SOLEIL ionized the samples above the S 2p edge, at 171 eV. Cationic species resulting from the photoionization process were analyzed according to the ejected electrons binding energy. NEXAFS measurements of both molecules in the S 2p edge were obtained and will be compared to theoretical results. 

A. Giertz et al., J. Chem. Phys., 117, 7587, 2002.

E. Kukk et al., Phys. Rev. A, 91, 043417, 2015.

J. B. Martins, Thèse de Doctorat, Sorbonne Université, 2021.

E. Kukk et al., Phys. Rev. Research, 3, 013221, 2021.

M.L. Rocco et al., Surface Sciences, 560, 45, 2004.

J.R. Santa Rita et al., J. Elec. Spectr. Relat. Phenom. 184, 265, 2011.

J. Eigenbrode et al., Science, 360, 1096, 2018.

J. Heinz and D. Schulze-Makuch, Astrobiology, 30, 552, 2020.   

Relaxation and non-RPA Effects in Photoionization Time Delay of Ar 3s and 3p subshells

Photoionization studies of the inner and outer subshells of atomic argon have been extensively reported in literature [1-6]. Photoionization cross sections, angular distribution asymmetry parameter, branching ratios, phase of the matrix elements and the photoionization Wigner time delay for argon have been reported at using different computational techniques [1-6]. Alexandridi et al., [6] have reported the experimental results of atomic delay difference between the 3s and 3p subshells of argon in the region of 3s (38 eV – 45eV) and 3p (45eV to 60eV) Cooper Minimum (CM) photon energy. A discrepancy between the experimental data and the theoretical calculations using 2P2C RPAE technique [6] is observed to be more significant in the region of 3s CM when compared to the region of 3p CM. The present work aims to calculate the photoionization time delay in this energy range of argon in the presence of relaxation effects using RRPA- R approximation [7], and non-RPA correlations using the RMCTD [8-9] approximation. It is predicted that inclusion of important non-RPA correlations improves the agreement with experimental results and help understand the dynamics of argon photoionization. Ref: [1] D.J. Kennedy and S.T. Manson Phy. Rev. A, 5 (1972). [2] R.G. Houlgate et al., J.Phys. B, 7 (1974) [3] M. Kutzner et al., Phy. Rev. A, 55 (1997) [4] A. Kheifets et al., Phys. Rev. A 94, 2016 [5] S. Saha et al., Phys. Rev. A, 90 (2014) [6] C. Alexandridi et al., Phys. Rev. Research, 3 (2021) [7] V. Radojevic, et al., Phys. Rev. A 40 727-734 (1989) [8] V Radojevic and W. R. Johnson Phys. Rev. A 31, 2991 (1985). [9] Jose J et al., Phys. Rev. A83 053419 (2011).   

Enhancement of database NORAD-Atomic-Data for atomic processes in plasma

We report recent enhancements of the online atomic database at the Ohio State University, NORAD-Atomic-Data, that provides various parameters

for radiative and collisional atomic processes dominant in astrophysical plasma. NORAD stands for Nahar Osu RADiative. The database belongs to the data sources, especially for the latest works, of the international collaborations of the Opacity Project and the Iron Project. The contents of the database are calculated values for energies, oscillator strengths, radiative decay rates, lifetimes, cross sections for photoionization, electron-ion recombination cross sections and recombination rate coefficients. We have recently expanded NORAD-Atomic-Data with several enhancement as follows.  i) We continue to add energy levels, transition parameters,

cross sections for atoms and ions with their publications. ii) Recently added radiative atomic data contains significant amount of transition data for photo-absorption spectral features corresponding to x-ray resonance fluorescence effect, prominent wavelength regions of bio-signature elements, such as phosphorus ions, and emission bumps of heavy elements, such as of lanthanides, that may be created in a kilonova event. We are including iii) collisional data for electron-impact-excitation, iv) experimental data for energies and oscillator strengths for line formation, v) experimental cross sections for photoionization that can be applied for benchmarking and other applications, and vi) introduction of a web-based interactive feature to calculate spectral line ratios at various plasma temperature and density diagnostics, starting with our recently published data for P~II. We present a  summary description of theoretical backgrounds for the

computed data and of measurement of high resolution photoionization cross sections at Advanced Light Source of LBNL synchrotron set-up and briefly discuss other set-ups. These additions should make NORAD-Atomic-Data more versatile for various applications.   

Higher order non-dipole effects in the angular distribution and spin polarization of photoelectrons from sodium 3s in the vicinity of the dipole Cooper minimum

The impact of electric-dipole and electric-quadrupole interference terms (E1-E2) on the photoionization dynamics of Na 3s subshell, in the vicinity of dipole Cooper minimum, was analyzed in our recent work [1]. We have now extended this work by including second order non-dipole corrections to the dynamics. The calculations now include contributions from electric-quadrupole/electric-quadrupole (E2-E2) and electric-dipole/electric-octupole interference terms (E1-E3). The non-dipole parameters are derived from the general formulation of angular distribution of photoelectrons developed by Keh-Ning Huang [2, 3]. A combination of GRASP [4-5] and RATIP [6] packages are employed to obtain the required transition amplitudes. Furthermore, we explore the effect of higher order non-dipole interactions on the spin polarization of emitted photoelectron.

References

[1] Hosea, N. M., et.al., Atoms 2023, 11, 125.

[2] Huang, K. N., Physical Review A 1980, 22, 223.

[3] Huang, K. N., Physical Review A, 1982, 26, 3676.

[4] Parpia, F. A., et.al., Computer Physics Communications, 1996, 94, 249.

[5] Jönsson, P., et.al., Computer Physics Communications, 2013, 184, 2197.

[6] Fritzsche, S., Computer Physics Communications, 2012, 183, 525.   

R-Matrix calculations for opacities: IV.: Convergence, completeness, and comparison of relativistic R-matrix and distorted wave calculations for Fe xvii and Fe xviii

To investigate the completeness of coupled channel (CC) Breit-Pauli R- Matrix (BPRM) calculations for opacities, we employ the relativistic distorted wave

(RDW) method to complement (“top-up”) and compare the BPRM photoionization cross sections for high-nl levels of both Fe xvii and Fe xviii . Good agreement is found in background photoionization cross sections using these two methods, which also ensures correct matching of bound level cross sections for completenss. In order to top-up the CC-BPRM calculations, bound-bound transitions involving additional bound levels, and a large number of doubly-excited quasi-bound levels corresponding to BPRM autoionizing resonances described in paper II, are calculated using the RDW method. Photionization cross sections in the high energy region are also computed and compared up to about 500 Ry, and contributions from higher core level excitations than BPRM are considered. The effect of configuration interaction is investigated, which plays a significant role in correctly reproducing some background cross sections. Owing to the fact that the additional RDW levels correspond to high-nl bound levels that are negligibly populated according to the Mihalas-Hummer-Däppen equation-of-state

(paper I), the effect on opacities is expected to be small.   

Plasma Broadening of Autoionizing Resonances

 A general formulation is developed to study and quantitatively ascertain the effect of plasma broadening of intrinsic

autoionizing (AI) resonances in photoionization and electron-ion scattering cross sections. In particular, R-matrix data for iron ions described in a paper in the RMOP series (RMOP-II, hereafter RMOP2) are used to demonstrate underlying physical mechanisms due to electron collisions, ion microfields (Stark),

thermal Doppler effects, core excitations, and free-free transitions. Breit-Pauli R-matrix (BPRM) cross section for the large number of bound levels of Fe ions are

considered, 454 levels of Fe~XVII, 1,184 levels of Fe~XVIII and 508 levels of Fe~XIX. Following a description of theoretical and computational methods, a sample of results is presented to show significant broadening and shifting of AI resonances due to extrinsic plasma broadening as a function of temperature and density.

Redistribution of AI resonance strengths broadly preserves their integrated strengths as well as the naturally intrinsic asymmetric shapes of resonance complexes which are broadened, smeared and flattened, eventually dissolving into the bound-free continua. The impact on plasma opacities is discussed.   

Rovibrational transitions in OH due to collisions with He

In this work, we present scattering calculations for rovibrational transitions of OH(X²Π) induced by collisions with He in which fine-structure and Λ-doubling are incorporated dynamically. Rate coefficients for rotationally inelastic transitions of OH(v=0) induced by He have been computed previously for j≤11.5 [Klos et al., Chem. Phys. Lett, 445, 12 (2007)]. The present work extends previous calculations to include rates for vibrational de-excitation from OH(v=1,j). A quantum close-coupling method was used for selected j at temperatures between 1 and 500 K. The coupled-states approximation, which is less computationally intensive, was used for j=0.5-10.5 for temperatures between 1 and 3000 K; these rates were benchmarked against the close-coupling results. 

The hydroxyl radical is a key species in the water chemistry of star-forming regions, and recent observations from the James Webb Space Telescope include spectra corresponding to the fundamental OH rovibrational band. The state-to-state rate coefficients presented here are needed to interpret spectra taken from non-local thermodynamic equilibrium (NLTE) environments.   

Ionization and dissociation of acetonitrile by proton collision

Nitriles, like acetonitrile (H₃CCN), are organic compounds found in planetary atmospheres and in the interstellar medium. This study focuses on dissociative ionization processes induced by proton collisions from 40 keV to 155 keV on gaseous nitriles, The selected energy range matches that of protons incident on the Earth's atmosphere. Pulsed proton beams collide with nitriles molecules in a gas cell under ultra-high vacuum conditions. The cations are analysed using a high-resolution reflectron spectrometer. Experimental results provide insights into fragmentation channels and formation yields, aiding in understanding chemical processes in various environments. Absolute cross-sections are obtained by normalization to the total theoretical ionization cross-section calculated by CTMC and CDW-EIS. The study offers insights for stellar object chemistry and molecule half-life determination.

Reference

H. Abdoul-Carime et al.  ACS Earth and Space Chemistry 6, 4, 1126-1132 (2022)

M. Bulak et al. A&A 647, A82 (2021)

C. Ceccarelli et al.  arXiv:2206.13270 (2022)   

Elastic Scattering Studies of Fullerenes and its Derivatives

The present work explores the low energy elastic electron scattering from fullerenes and its derivatives. We simulate these fullerenes, C₆₀,C₂₄₀ and the nested fullerene C₆₀@C₂₄₀, by using the well established annular square well(ASW) potential [1]. The static ASW model is relatively easy to implement compared to robust molecular-level models [2]. Despite the simplicity, the static ASW model has been successful in unravelling the qualitative features associated with the scattering dynamics of fullerene molecules in the past. The combined system, C₆₀@C₂₄₀, is modeled by summing the two model potentials directly [3]. The focus of the present work is on identifying the differential cross-section details along with the time delays involved in the scattering process both in the resonant and non-resonant regions.   

Absolute partial and total electron impact cross sections of fluorine and chlorine based atmosphere-damaging molecules

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons  (HCFCs) molecules pose a serious environmental threat [1].  Once released into the earth  atmosphere, they accumulate in the stratosphere, where they contribute to the depletion of the ozone layer.  Reactions that may occur in the stratosphere were detailed in the literature [2]  . Here we present experimental non-dissociative and dissociative cross-sections for electron impact of CFCs and HCFCs atmosphere-damaging molecules. The experiments, based on a Reaction Microscope (ReMi), were carried out at several electron energies up to 1 keV. A noble gas and CFC (HCFC) mixing setup was implemented to convert the relative cross sections measured by the ReMi setup into absolute values. Using these techniques, ion collection and calibration uncertainties  were minimized. The presented results on CF₄ and  HCFCs were compared with theoretical and experimental studies available in the literature [3,4]. Previous electron impact experiments mostly present relative cross sections and add simulated corrections to obtain the absolute cross sections due to the difficulty in the determination of absolute data. We elucidate the differences of the new measurement method from the existing ones in the literature and explain why the new method is needed. Further we show how reducing correction terms affects the results obtained.

References

1 L. M. Western et al. , Nat. Geosci. 16, 309–313 (2023).

2 Scientific Assessment of Ozone Depletion, Chapter 2: Hydrofluorocarbons, (2022).

3 L. G. Christophorou, J. K. Olthoff and M. V. V. S. Rao J. Phys. Chem. Ref. Data 25, 1341–1388 (1996).

4. L. G. Christophorou and J. K. Olthoff, J. Phys. Chem. Ref. Data 28, 967–982 (1999).   

Reconstruction of one and two-photon atomic ionization amplitudes from multicolor RABBITT measurements

The delay in the one-photon ionization of atoms is encoded in the photoionization-amplitude phase [1]. A well established technique to recover this phase is the Reconstruction of Attosecond Beating By Interference of Two-photon Transitions (RABBITT), which utilizes an attosecond pulse train (APT) pump in association with an IR probe pulse with controllable delay [2]. In RABBITT, the phase difference between the photoelectron amplitudes generated by consecutive odd harmonics is inferred from the interference of their common sideband, based on assumptions on the continuum-continuum (cc) radiative-transitions delay [3]. Angularly-resolved measurements can give access to the angular dependence of the time delay [4] as well as to the delay for the emission of photoelectrons with different orbital angular momenta [5]. By measuring also the beatings between two-photon and one-photon paths, it is possible to circumvent the need of using analytical values for the cc delay [6].  In this work, we present a numerical analysis of an alternative method to extract both one-photon and two-photon amplitudes for a given atomic target. The method combines data from two angularly resolved RABBITT measurements that employ the same APT and either the fundamental or the second harmonic of the IR pulse as a probe. Using Monte Carlo simulations, we determine the range of all the relevant one-photon and two photon amplitudes that are compatible with the baseline, amplitude and phase of the asymmetry parameters of both harmonic and sideband signals, measured with realistic uncertainties. This approach offers a novel pathway for disentangling complex photoionization dynamics.

[1] R. Pazourek et.al., Rev. Mod. Phys. 87, 765 (2015).

[2] K. Kl ̈under et.al., New J. Phys. 106 143002 (2011).

[3] J. M. Dahlstr ̈om et al., J. Phys. B: At. Mol. Opt. Phys. 45, 183001 (2012).

[4] S. Heuser, Phys. Rev. A 94, 063409 (2016).

[5] J. Peschel et.al., Nat. Comm. 13 5205 (2022)

[6] J. Fuchs et.al., Optica 7 154 (2020)   

Revolutionizing Additive Manufacturing with Magnetic Fields: Fabricating Intelligent Bimetals

This research transforms additive manufacturing (AM) by integrating engineered magnetic fields for the direct production of intelligent bimetallic structures, focusing on Nitinol (NiTi) and stainless steel (SS). The Magnetic Field-Assisted Additive Manufacturing (MF-AM) process uses magnetic fields during laser-based techniques to control intermetallic compound formation.

The project aims to inhibit brittle intermetallic compounds at the NiTi/SS interface, enhancing interfacial adhesion, and explore the magnetic field's influence on NiTi microstructure for improved multi-directional functionality. It contributes to computational methodologies for microstructure-sensitive process design, offering profound insights into process parameters and mechanical property modifications.

Anticipated outcomes include academic publications, presentations, and workshops, enriching the scientific community's understanding of Magnetic Field-Assisted Additive Manufacturing advancements.   

Exploring Asymmetry in Photoangular Distributions through Multi-Channel Interference

In the realm of coherent control of ultrafast strong field interactions, the manipulation and understanding of photoangular distributions (PADs) are crucial for advancing control

mechanisms at the quantum level. This presentation discusses the significance of asymmetry in these distributions, a phenomenon that reveals fundamental aspects of quantum interference.

In this presentation we explore numerical solutions of the Time-Dependent Schrodinger Equation (TDSE) which hint at one method in which asymmetry may be induced,

and potentially controlled. Specifically, the results display how tuning the non-perturbative intensity parameter z = U_p/ω (where U_p is the pondermotive energy and ω is laser frequency) and may prescribe asymmetry in the angular distributions where notable yield is observed. This is achieved through the opening of two or more channels whose interference patterns are angle dependent, therefore disrupting any symmetries previously present. Tuning of these patterns may allow for significant control over both the spectral as well as spatial distributions of photoelectrons, furthering our ability to control, image, and understand ultrafast processes.

    

Fragmentation dynamics of fullerenes upon extreme electronic excitation near the giant resonance with XUV free-electron laser pulses

Fullerenes serve as an ideal model system to investigate the complex dynamics in large molecules, which often exhibit a complex interplay of single- and many-body phenomena. The strong coupling between dense electronic states and phonon modes in fullerenes leads to complex energy absorption and dissipation pathways. We explore these processes by leveraging the collective resonance of C₆₀ to deposit a large amount of energy through intense XUV radiation from the FLASH free-electron laser over ultrashort timescales. Using a single-color pump-probe scheme, we measured the kinetic-energy spectra of both light and heavy ionic fragments as a function of the pump-probe delay. Our theoretical modeling revealed the formation of a transient nanoplasma, which explains the distinctive delay dependence of the doubly-charged carbon yield. Furthermore, this model is consistent with the Wigner threshold behavior observed in the kinetic-energy distributions of monomer and dimer ions.   

Attosecond probing of nuclear vibrations in the D2+ and HeH+ molecular ions

We study the ultrafast photodissociation of small diatomic molecules using attosecond laser pulses of moderate intensity in the XUV regime. The simultaneous application of subfemtosecond laser pulses with different photon energies - resonant in the region of the molecular motion - allows one to monitor the vibrational dynamics of fast diatomics, like the D2+ and HeH+ molecular ions (Biró and Csehi, accepted in J. Phys. Chem. A). In our real-time wave packet simulations, the nuclear dynamics is initiated either by sudden ionization (D2+) or by explicit pump pulses (HeH+) via distortion of the potential energy of the molecule. The application of time-delayed attosecond pulses leads to the breakup of the molecules. The information on the underlying bound-state dynamics is imprinted in the kinetic energy release (KER) spectra of the outgoing fragments (Phys. Chem. Chem. Phys. 24, 13234, 2022). We show that the KER-delay spectrograms generated in our ultrafast pump-probe schemes are able to reconstruct the most important features of the molecular motion within a given electronic state, such as the time period or amplitude of oscillations, interference patterns, or the revival and splitting of the nuclear wave packet.   

Synthetic nanoscale quantum emitter rings for efficient excitation transport

Light-harvesting complexes (LHCs) are composed of rings of chromophores. They efficiently collect and transport solar energy to the photosynthetic reaction center. To explain this photo-physics, one could model them as sub-wavelength rings of optical dipoles, which support dark eigenmodes and exhibit efficient excitation energy transfer [1-4]. We present a theoretical investigation of the optical properties of coupled few-emitter nanoscale ring geometries, which offer insights into achieving synthetic LHCs with state-of-the-art experimental techniques and understanding the extraordinary optical properties of natural LHCs. Our study opens up scopes to harness solar energy with a diverse class of coupled rings, for example, utilizing controlled geometry of quantum dots and crafting inter-node loss-less links in a quantum network.

[1] M. Moreno-Cardoner et al., Phys. Rev. A 100, 023806 (2019).

[2] J. A. Needham et al., New J. Phys. 21, 073061 (2019).

[3] V. Scheil et al., Nanomaterials 13, 851 (2023).

[4] R. Holzinger et al., arXiv:2309.11376 (2023).   

Vibrational excitation influence in a chemical laser based on polyatomic chemical reaction dynamics

The author's research focuses on a polyatomic reaction in the gas phase, OH + D₂ ---> HOD + D. He uses Quasi-Classical Trajectory (QCT) methodology on Wu-Schatz-Lendvay-Fang-Harding (WSLFH) potential energy surface (PES) [1] because it is one of the best PES for this study. The amplitude of the samples, allows to obtain clarifying results that confirm previous researches [2] and show future experimental targets. Author uses Gaussian Binning (GB) methodology to show in a better way a variable preference in values of the Total Angular Momentum (J’) of excited product molecule, HOD*((v_HO’, v_HOD’, v_OD’), J’). One of his present intention is studying dynamics of this chemical reaction, because of its significance in the processes of excitation and emission in a posible chemical laser based on that reaction. The increase of the vibrational level, v , in one of the reactives, D₂ (v = 0, 1, 2, 3, 4; j = 2), induces a significative increase of the mentioned excitation, HOD*, and a displacement of the distributions, P(J'), towards higher values of J', but a greater dispersion of this distribution. Althought j = 2 is the initial condition is fixed in the present study, author pretends to amplie their researchs for a more amplie espectrum of posible initial conditions in the reaction camera.

 

References

[1] J. Chem. Phys., 2000, 113, 3150.

[2] DOI: 10.1117/12.2518606.   

Nonlinear features of UV laser-induced excitonic luminescence in ZnO nanopowder

ZnO is one of the best photoactive wide-gap metal-oxide semiconductor materials, whose optical and electronic properties are of great interest for modern nanophotonics and quantum electronics [1,2]. In particular, photoexcited ZnO exhibits excitonic photoluminescence (PL) in the near UV spectral range even at room temperature (RT). But despite advances in ZnO nanophysics and nanotechnology, some features of RT excitonic PL of ZnO nanoparticles (NP) are not so clear, especially in disordered nanostructures with random light scattering, such as nanopowder. We tried to study this issue in more detail. Experiments were carried out with fine-disperse ZnO powders of high grade quality obtained by hydrothermal process and characterized by XRD, SEM, Raman and UV-visible spectroscopy. Measurements showed that ZnO NPs have a nodular shape with sizes from 1 μm to 100 nm and nanocrystallites of ~20 nm. In the PL spectra excited in ZnO powder layers by a pulsed N₂ laser at 337 nm, we observed a nonlinear amplification of excitonic UV PL emission with a maximum at 387 nm and a decay of the relatively weak visible PL emission with a maximum at 500 nm. A superlinear growth in the intensity of the excitonic UV PL band with its narrowing with increasing excitation intensity indicates stimulated emission with incoherent feedback in the ZnO nanopowder. This regime is realized over the entire excitation range due to non-resonant diffusion mode of optical amplification, similar to random lasing in Letokhov-type scattering photonic media. Estimated gain is ~100 cm^-1, threshold is ~1 mJ/cm². The results look promising. Research is in progress. [1] A. Tashiro, Y. Adachi, T. Uchino, J. Appl. Phys. 133, 221101 (2023). [2] H. Cao, Y. Eliezer, Appl. Phys. Rev. 9, 011309 (2022).   

Efficient quantum state transfer in coupled levitated nanoparticle system

 Sandeep Sharma^{1, *}, Seongi Hong¹, and Andrey S. Moskalenko<sup>1

1</sup>Department of Physics, KAIST, Daejeon 34141, South Korea

 

Successful trapping and levitation of two or more nanoparticles have opened up a new avenue for exploring many-body physics such as coherent manipulation of quantum states, entanglement dynamics, tunable quantum sensing, and nonequilibrium physics using these systems [1].

We report on the creation and transfer of different quantum states in a system of two interacting levitated nanoparticles. The nanoparticles are levitated using two distinct optical tweezers and interact with each other via the scattered fields of the trapping lasers constituting the tweezers. We create a squeezed thermal state in the mechanical mode of one nanoparticle, and then by suitably changing the trapping laser phases and the inter-particle distance, we transfer it to the other nanoparticle with very high fidelity. Further, we confirm this high transfer fidelity rate by creating and transferring a coherent state as well. Our work may have potential application in quantum information processing.

 

[1] J. Rieser, M. A. Ciampini, H. Rudolph, N. Kiesel, K. Hornberger, B. A. Stickler, M. Aspelmeyer, and U. Delić, Science 377, 987 (2022).   

Spectral properties and observables in ultracold Fermi gases

We calculate non-perturbative self-consistent fermionic and bosonic spectral functions of ultracold Fermi gases directly in real-time. The spectral functions are then used for the determination of the equation of state, the Tan contact and ejection rf spectra at unitarity. These results are compared to experimental data, the self-consistent T-matrix approach and lattice results. Our approach offers a wide range of applications, including the ab initio calculation of transport and spectral properties of the superfluid phase in the BCS-BEC crossover.   

Ultra-tight confinement of atoms in Rydberg quantum lattice

 Tight confinement of single sites in conventional lattices requires excessive laser intensity which in turn suppresses the coherence. This talk proposes a scheme for atomic lattice with sub-wavelength structure. The atom-light coupling combined with Rydberg interaction has opened a wide range of applications in quantum technology [1-11]. This presentation utilises the nonlinear optical response of the three-level Rydberg-dressed atoms to form ultra-narrow trapping potentials [12]. The lattice consists of a 3D array of ultra-narrow Lorentzian wells with sub-nanometer widths.The interaction-induced two-body resonance that forms the trapping potential [13], only occurs at a peculiar laser intensity, localizing the trap sites to ultra-narrow regions over the standing-wave driving field.  The tight confinement is desired for quantum logic operations with Rydberg-Fermi interaction [14-15] and  quantum walks [16].

 

References:

[1]M. Khazali, K. Mølmer, Phys. Rev. X 10, 021054 (2020).

[2]M. Khazali, Phys. Rev. A 98, 043836 (2018)

[3]M. Khazali, H. W. Lau, A. Humeniuk, C. Simon, Phys. Rev. A 94, 023408 (2016)

[4]M. Khazali, K. Heshami, C. Simon, Phys. Rev. A 91, 030301 (2015)

[5]M. Khazali, C. Murry, T. Pohl, Phys. Rev. Lett. 123, 113605 (2019)

[6]M. Khazali, K. Heshami, C. Simon J. Phys.  B, 50, 21 (2017)

[7]M. Khazali, Optics Express 31(9), 13970-13980 (2023)

[8]H Kaviani, et. al, New J. Phys. 15, 085029 (2013)

[9]M. Khazali, IJAP 10, 19 (2021)

[10]Khazali, Mohammadsadegh. "Applications of Atomic Ensembles for Photonic Quantum Information Processing and Fundamental Tests of Quantum Physics." Ph.D. thesis, University of Calgary (2016)

[11] Khazali, Mohammadsadegh. "Fast generation of multi-component cat states under the Strong Rydberg Dressing Regime." arXiv preprint arXiv:2312.11432 (2023)[12]Khazali, M. (2023). Subnanometer confinement and bundling of atoms in a Rydberg empowered optical lattice. arXiv preprint arXiv:2301.04450

[13]M Khazali, Phys. Rev. Research 3, L032033 (2021)

[14]Khazali, M., & Lechner, W. Communications Physics 6, 57 (2023)

[15]Khazali, M. (2022).  arXiv preprint arXiv:2204.08522

[16]M. Khazali, Quantum 6, 664 (2022)   

Measurement of the static Stark Shift of the 7s 2S1/2 level and a reevaluation of the vector Stark polarizability on the 6s 2S1/2→7s 2S1/2 transition in atomic cesium.

Measurements of atomic parity violation (APV), mediated by the weak interaction, facilitate determinations of the weak charge Q_w, as well as the weak mixing angle, θ_w. These values provide a unique test of the standard model at low momentum transfers. Determination of Q_w relies on theoretical calculations as well as precision measurements of a parity-violating optical transition relative to another known transition. The most precise measurement of APV was that of Wood et al. [1], who measured the ratio of the parity non-conserving (PNC) transition amplitude (E_PNC) relative to the vector Stark polarizability (β) in atomic cesium. Contention between the two techniques that are used to determine β, see [2], requires resolution for precise determination of Q_w. Here we discuss our recent efforts to correct the discrepancy including a measurement of the dc Stark shift of the 7s  ²S_1/2 state in atomic cesium [3]. We measure the Stark shift by offset phase locking a laser to a frequency comb source and drive a Doppler free two-photon transition. We use theoretical calculations of Tan et al. [4] (for E1 matrix elements to high n states) to recalculate the 〈7s‖r‖7p_1/2〉and 〈7s‖r‖7p_3/2〉  reduced dipole matrix elements and then use these new matrix elements to reevaluate β.

[1] C. S. Wood, S. C. Bennett, D. Cho, B. P. Masterson, J. L. Roberts, C. E. Tanner, and C. E. Wieman, Science 275, 1759 (1997).

[2] G. Toh, A. Damitz, C. E. Tanner, W. R. Johnson, and D. S. Elliott, Phys. Rev. Lett. 123, 073002 (2019).

[3] J. Quirk, A. Jacobsen, A. Damitz, C. E. Tanner, and D. S. Elliott,  arXiv:2311.09169 (2023).

[4] H. B. Tran Tan and A. Derevianko, Phys. Rev. A 107, 042809 (2023).   

Technique for a direct measurement of the cesium anapole moment using coherent rf and Raman interactions

We report progress toward measurements of the electric dipole (E1) transition moments between hyperfine components of the ground state of atomic cesium. This transition is weakly E1 allowed due to weak interactions between nucleons within the nucleus, which lead to a parity-odd current distribution and its associated anapole moment. In this report, we discuss the experimental geometry of our measurement scheme, explore the effects of extraneous fields that can obscure the signal, present initial measurements, analyze the sources and magnitudes of measurement noise, and suggest improvements to the current apparatus.   

Simulation of ultrafast methyl iodide photodissociation followed by Coulomb explosion using multi-reference methods

Coulomb explosion imaging (CEI) is a powerful tool for monitoring molecular structure changes during a chemical reaction. We present a direct simulation of methyl iodide photodissociation followed by Coulomb explosion, mirroring a recent pump-probe experiment utilizing coincident ion momentum imaging [1]. Our simulation is conducted on pre-built potential energy surfaces using an efficient molecular dynamics program. These surfaces are constructed based on accurate electronic structures calculated using the multi-reference configuration interaction method. We provide a direct comparison with the experiment for the delay-dependent kinetic energy release (KER) signals. Additionally, we discuss the effectiveness and potential challenges of using CEI to map conical intersections in coordinate space.

[1] F. Ziaee et al., Phys. Chem. Chem. Phys.  25, 9999 (2023)   

Prospects for quantum simulations with mixed species crystals in Penning traps

Penning traps are now an established platform for quantum science experiments with tens to hundreds of ions. Such experiments have typically employed a single trapped ion species. The inclusion of multiple ion species can lead to the emergence of novel crystal geometries and normal mode properties that may enable new classes of quantum science experiments in Penning traps. In this work, we study the equilibrium structure and normal modes of crystals formed by two species of ions co-trapped in a Penning trap. We observe that, under specific conditions, the ions organize into a 2D planar crystal, with the heavier ions forming a clean, well-separated ring at the crystal boundary. This finding opens avenues for studying spin models with closed and periodic boundary conditions. When the trapping conditions are scanned across the one-to-two plane transition point, the lighter ions in the crystal interior form a 3D crystal, while the heavier ions can still be confined to a planar ring. Under these conditions, some of the axial normal modes of the ring acquire a chiral nature, potentially enabling interesting opportunities for quantum simulations. Finally, the addition of an anharmonic trapping potential leads to all the lighter ions forming a clean bilayer geometry, which is stabilized by the ring of heavier mass ions. Our study demonstrates the potential for diversifying quantum simulation applications of Penning traps by utilizing more than one species of ions.   

Search for Exotic Long-Range Spin-Dependent Interactions with Dressed Atoms

Landé factor quantifies particle responses to magnetic fields, and is an essential parameter for quantum precision measurements. We propose a technique to actively manipulate the Landé factor based on the dressing effect of radio-frequency (rf) magnetic fields. We demonstrate a magnetic-field-insensitive system in which the frequency of the rf field is comparable to the spin-exchange (SE) rate of atoms, and the field strength is strong enough. Despite the system is insensitive to magnetic fields, it remains sensitive to exotic spin-dependent interactions. By utilizing magnetic-field-insensitive Zeeman resonances, we search for the non-magnetic long-range spin-dependent interaction V₉₊₁₀ of protons. The constraint on the long-range monopole-dipole interaction V₉₊₁₀ between protons of alkali-metal atoms and nucleons of the Earth is enhanced by an order of magnitude, reaching 4.2×10^-33. This method motivates a deeper understanding on the SE collision mechanism and offers a novel approach to search for spin-dependent interactions.   

Diagnostics of collisional flowing plasma using flat Langmuir probe

A continuum flat Langmuir probe has been developed to diagnose collisional flowing plasma ignited in atmospheric conditions. At atmospheric pressure, collisions between neutral and charged particles in plasma dominate since the ion-neutral mean free path is now exceedingly small compared to the sheath thickness and probe characteristic size. Collisions with atoms and molecules will serve as a friction force, slowing the charged particles as they accelerate towards the probe surface, affecting current collection. Therefore, conventional Langmuir probes does not work effectively. Hence the idea of using flat probes has been conceived. Moreover, placing the probe directly in the downstream zone causes extra filamental discharges and changes the plasma properties. Therefore, to characterize the jet plasma without changing its original nature, a half cylindrical vacuum chamber has been built and a sample of plasma plume is taken from atmosphere into the 100mbar vacuum chamber where the flat probe is placed. Experiments with various Langmuir probe setups were carried out. The IV curve was extracted using a double copper-cladded flat plate configuration with a 5mm separation and the plasma parameters were extracted using a continuum flowing plasma theory. The number density of electrons in plasma is calculated to be 5.3×10¹⁶ m^-3, and the electron temperature inferred from the curve is around 6.1 eV. The Druyvesteyn electron energy distribution function shows there are enough high-energy electrons in the plasma to trigger various chemical processes, which is important in plasma processing.   

Towards superfluid flow experiments with periodic boundry conditions.

We report on progress toward studies of superfluid flow in a uniform ring geometry realized on the surface of a cylinder.