Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session AAA04: V: Spectroscopy and Experiment in Chemical Physics |
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Sponsoring Units: DCP Chair: Xingjian Wang, University of Alabama in Huntsville Room: Virtual Room 4 |
Wednesday, March 22, 2023 12:30PM - 12:42PM |
AAA04.00001: Effect of a Solute on Critical Opalescence in a Binary Liquid Mixture Xingjian Wang, James K Baird, Christopher M Lyons The fluctuations in refractive index that occur near the critical point of a binary liquid mixture with a miscibility gap are the source of Rayleigh scattering of the incident light, resulting in a phenomenon known as “critical opalescence”. The refractive index oscillations are caused by fluctuations in the composition of the mixture, which are exaggerated at the critical point due to the mathematical divergence of the thermodynamic derivative that determines mixing. According to the Principle of Critical Point Universality, which is thought to govern all critical phenomena, this derivative is expected to diverge under conditions where the liquid mixture is at equilibrium at a fixed temperature, fixed pressure, and at the fixed composition characteristic of the critical point. The addition of a completely soluble solute to the mixture has the effect of introducing a second fixed composition variable. As predicted by the universality principle, the thermodynamic derivative governing mixing remains finite under such conditions. This finite behavior has the effect of quenching the critical opalescence. We have successfully tested this principle by observing the quenching of critical opalescence in the case of a variety of binary liquid mixtures to which various soluble solutes have been added. Despite the chemical diversity of the substances chosen, we have observed the suppression of critical opalescence without any exceptions. |
Wednesday, March 22, 2023 12:42PM - 12:54PM |
AAA04.00002: Vibrational energy levels and predissociation lifetimes of the A2Σ+ state of SH/SD radicals by photodissociation spectroscopy Jingsong Zhang, Yuan Qin, Xianfeng Zheng, Yu Song, Ge Sun Photo-predissociation of SH and SD radicals in the A2Σ+ state is investigated using the high-n Rydberg atom time-of-flight (HRTOF) technique. By measuring the photoproduct translational energy distributions as a function of excitation wavelength, contributions from overlapping A2Σ+ (v') <!--[if gte msEquation 12]>? X2Π (v") transitions can be separated, and the H/D + S(3PJ) photofragment yield (PFY) spectra are obtained across various rovibrational levels (SH v' = 0-7 and SD v' = 0-8) of the A2Σ+ <!--[if gte msEquation 12]> style='font-size:12.0pt;mso-bidi-font-size:11.0pt;line-height:107%;font-family: |
Wednesday, March 22, 2023 12:54PM - 1:06PM |
AAA04.00003: Cyanophenylalanine structural reconfiguration induced by ion binding: Magnesium-specific nitrile chelation motif in M2+ complexes Sean C Edington, Ahmed Mohamed, Mark A Johnson Noncoded amino acids are widely used as spectroscopic probes of complex biological systems. Para-cyanophenylalanine has found particularly broad use as a fluorescence, FRET, and infrared probe of protein structure and function. For example, its nitrile stretching absorption provides a readout of the electrostatic environments important to enzyme catalysis in a region of the infrared spectrum free from interference from other transitions. However, in complex systems it is often challenging to separate the spectral contributions from effects of interest, such as active pocket environment, from other factors like probe isomerization. |
Wednesday, March 22, 2023 1:06PM - 1:18PM |
AAA04.00004: Determination of the Size-Dependent Temperature Onsets for Long Range, Water-Mediated Proton Transfer in Microhydrated 4-Aminobenzoic Acid Thien T Khuu, Santino Stropoli, Abhijit Rana, Sean C Edington, Mark A Johnson Water-mediated translocation of “excess” protons is the basis of the well-known “Grotthuss” or proton-relay mechanism that accounts for the enhanced proton mobility that is observed in water. Here we report the temperature onset for spontaneous transfer of a proton between the two isomers (protomers) formed upon protonation of 4-aminobenzoic acid (H+4ABA). This is accomplished by isolating size-selected water clusters of H+4ABA in a temperature-controlled, radiofrequency ion trap and photodepleting one of them (the isomer protonated at the acid group, denoted the O-protomer) by excitation of the electronic band unique to this species at ~310 nm. We then follow the spontaneous depletion of the isomer protonated at the amino group (the N-protomer) and repopulation of the O-protomer as functions of time and temperature. The relative isomer populations are monitored by recording the vibrational spectra of the ion ensemble after ejection from the ion trap into a double-focusing, tandem time-of-flight photofragmentation mass spectrometer. The temperature onset of large amplitude proton motion is observed to be strongly dependent on cluster size, becoming much lower as cluster size increases from three to six water molecules. |
Wednesday, March 22, 2023 1:18PM - 1:30PM |
AAA04.00005: Two-photon dissociation dynamics of the mercapto radical Jingsong Zhang, Yuan Qin, Xianfeng Zheng, Yu Song, Ge Sun Two-photon dissociation dynamics of the SH/SD radicals are investigated using the high-n Rydberg atom time-of-flight (HRTOF) technique. The H/D(2S) + S(1D) and H/D(2S) + S(1S) products are observed in the dissociation of the SH/SD radicals on the 22Π and B2Σ+ repulsive states, from sequential two-photon excitation via the A2Σ+ (v' = 0, J' = 0.5-2.5) state. The angular distributions of both H/D(2S) + S(1D) and H/D(2S) + S(1S) product channels are anisotropic. The anisotropy parameter (β) of the H(2S) + S(1D) products is ~ −0.8 ± 0.1 (−0.9 ± 0.05 for SD), and that of the H(2S) + S(1S) products is ~ 1.3 ± 0.3 (1.2 for SD). The anisotropic angular distributions indicate that the SH/SD radicals promptly dissociate on the repulsive 22Π and B2Σ+ potential energy curves (PECs) along with some non-adiabatic crossings, leading to the H/D(2S) + S(1D) and H/D(2S) + S(1S) products, respectively. The bond dissociation energy of the ground-state X2Π3/2 SH/SD to the ground-state H/D(2S) + S(3P2) products is measured to be D0(S−H) = 29253 ± 20 cm−1 and D0(S−D) = 29650 ± 20 cm−1, respectively. The dissociation energy of the A2Σ+ state SH/SD to the H/D(2S) + S(1D) products is derived to be D0[S−H(A)] = 7659 ± 20 cm−1 and D0[S−D(A)] = 7940 ± 20 cm−1. |
Wednesday, March 22, 2023 1:30PM - 1:42PM |
AAA04.00006: Polymer-like modes in shear mechanical spectra of phenylpropanols: The influence of hydrogen-bonded structures Mathias Mikkelsen, Jan P Gabriel We present a dielectric and shear mechanical study of 1-propanol and three phenylpropanols. |
Wednesday, March 22, 2023 1:42PM - 1:54PM |
AAA04.00007: Recent Developments in the Implementation of the RT-EOM-CC Green's Function Approach Fernando D Vila, Himadri Pathak, Ajay Panyala, Bo Peng, Nicholas P Bauman, Erdal Mutlu, John J Rehr, Karol Kowalski Many-body excitations in X-ray photoemission spectra (XPS) are difficult to simulate from first principles. We have recently developed[1] a non-linear cumulant real-time equation-of-motion coupled-cluster (RT-EOM-CC) Green's function method that provides a non-perturbative framework for treating these problems in molecular systems. Here we report the implementation of RT-EOM-CC with single and double excitations within the Tensor Algebra for Many-body Methods (TAMM) infrastructure. TAMM is a massively parallel heterogeneous tensor library designed for utilizing soon-to-be-available exascale computing resources. The two-body electron repulsion matrix elements are Cholesky-decomposed and imposed spin-explicit form while evaluating tensor contractions of matrix elements involving various operators. This new implementation also improves performance by directly supporting complex algebra unlike our earlier Tensor Contraction Engine (TCE) implementation. Other recent improvements include a novel, variable time approach for the solution of the recursive equations present in the first-order Adams-Moulton method used to propagate the time-dependent amplitudes. These improvements are demonstrated by a study of the XPS of the formaldehyde and ethyltrifluoroacetate (ESCA) molecules. Simulations of the latter are challenging, as they involve as many as 71 occupied and 649 virtual orbitals, yet the relative ionization potentials are in good agreement with experiment. |
Wednesday, March 22, 2023 1:54PM - 2:06PM |
AAA04.00008: Comparative study of the thermal properties of 10W30 engine oil at various temperatures by addition of nano-particles. Chanaka P Galpaya Engine oils are used as coolants and lubricants in different types of vehicles with the aim of maintaining the temperature of the engine and reducing friction between parts and their abrasion. The thermal properties of engine oil are the key parameters when selecting engine oil for a vehicle. This study is carried out to compare the effect of Fullerene (C60), TiO2 and Fe2O3 nano-particles with different mass fractions on the thermal properties of 10W30 engine oil. In this study, the effect of TiO2 and Fe2O3 nano-particles concentrations 0.05 wt%, 0.1 wt% and fullerene (C60) nano-particle concentration 0.01 wt% on 10W30 engine oil were examined at different temperature values (30 - 120 ?). The nano-fluids were prepared using direct mixing method. A surfactant (CTAB-0.05 wt%) was used to prevent the agglomeration. As the reference CTAB-engine oil sample also prepared for the measurements. The thermal properties namely, thermal conductivity, thermal diffusivity and volumetric heat capacity of the base fluids and nano-fluids were measured using the Flucon LAMBDA thermal conductivity meter (TECHNE UCAL 400+ dry-block calibrator, Germany) while flash point was measured using the flash point tester (Anton Paar PMA500, Germany). The experimental results reveal that the thermal properties of engine oil with TiO2 and Fe2O3 were significantly enhanced when increasing the mass fractions in contrast to fullerene-based nano-fluid was not shown such enhancements. |
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