Bulletin of the American Physical Society
Fall 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students
Volume 60, Number 15
Thursday–Saturday, October 29–31, 2015; Waco, Texas
Session C1: Atomic/Molecular Physics I |
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Chair: W. Ariyasinghe, Baylor University Room: C.105 |
Friday, October 30, 2015 10:45AM - 10:57AM |
C1.00001: All-collinear FAST CARS on gases Anton Shutov, Dmitry Pestov, Xi Wang, Ariunbold Gombojav, Alexei Sokolov, Marlan Scully The femtosecond adaptive spectroscopic technique for coherent anti-Stokes Raman spectroscopy (FAST CARS) aims to optimize the laser-pulse configuration for rapid detection and identification of chemicals. Using two ultrashort Stokes-pump preparation pulses in combination with a narrowband delayed probe pulse, provides perfect non-resonant four-wave mixing background suppression. For this reason, one can choose the time delay for the tailored probe pulse such that it overlaps the preparation pulses at the node. The high usability of the FAST CARS allows for real-time monitoring of various gases, for example, CO$_{\mathrm{2}}$, O$_{\mathrm{2}}$ and N$_{\mathrm{2}}$ concentrations in air. In our experiments, we used obtained CARS signal for O$_{\mathrm{2}}$ in the ambient air and in the test cell to perform various measurements. Oxygen cross-sections of CARS spectrogram were obtained, additionally we made concentrations measurements of oxygen and nitrogen mixture. Finally, it was shown how CARS signal can be used for imaging gas flow. [Preview Abstract] |
Friday, October 30, 2015 10:57AM - 11:09AM |
C1.00002: Ionization and dissociation of acetonitrile with intense laser pulses Y. Boran, A. A. Kolomenskii, M. Sayrac, H. A. Schuessler, J. Strohaber We present an experimental study of laser induced ionization and dissociation of acetonitrile molecule (CH$_{\mathrm{3}}$CN) by using a reflectron type time-of-flight (TOF) mass spectrometer. In these experiments an amplified ultrafast Ti:sapphire laser system emitting 50fs pulses of radiation centered at 800nm wavelength and having a 1kHz repetition rate was used. At the intensity of $3x10^{14}W/cm^{2}$ we observed singly charged ions CH$_{\mathrm{n}}$CN$^{\mathrm{+}}$ (n$=$0-3), CN$^{\mathrm{+}}$, CH$_{\mathrm{2}}^{\mathrm{+}}$, C$^{\mathrm{+}}$, and H$^{\mathrm{+}}$ as well as fragments with higher charge states C$^{\mathrm{2+}}$, C$^{\mathrm{3+}}$,CH$_{\mathrm{2}}^{\mathrm{2+}}$, and CH$_{\mathrm{2}}^{\mathrm{3+}}$ , when using both linear or circular polarizations of the driving field. We also present and analyze laser intensity dependences for the yields of the parent ion and other fragments ranging from $4.4x10^{13}W/cm^{2}$to $3.3x10^{14}W/cm^{2}.$ Finally, we investigated angular dependences of acetonitrile fragmentation by changing the polarization direction of the laser beam with respect to the TOF axis and concluded that yields of heavy fragments do not show strong angular dependences, while light fragments, especially with higher charge states, demonstrate a strong anisotropy. [Preview Abstract] |
Friday, October 30, 2015 11:09AM - 11:21AM |
C1.00003: Spectroscopic and Theoretical Investigations of the Conformations and ð-type Hydrogen Bonding of 2-Cyclohexen-1-ol Esther Ocola, Jaan Laane Infrared and Raman spectra of 2-cyclohexen-1-ol have been collected for its liquid and vapor states. As confirmed by \textit{ab initio} (MP2/cc-pVTZ) and density functional theory (B3LYP/cc-pVTZ) calculations, this molecule can exist as six different conformers, possibly only five, if the third most abundant conformer and the first most abundant conformer have no energy barrier between them. The conformers can interconvert by the twisting of the six-membered ring or by torsional rotation of the --OH bond. This can be shown by a potential energy surface and its topological map. The lowest energy conformers \textbf{A }and \textbf{B} have the --OH bond oriented towards the C$=$C bond and possess an intramolecular $\pi $-type hydrogen bonding. The calculated distance from the hydrogen atom of the --OH group to the middle of the C$=$C bond is 2.7 {\AA} for \textbf{A}, whereas for \textbf{B} it is 3.0 {\AA}. The highest energy form lies 401 cm$^{\mathrm{-1}}$ (1.15 kcal/mol) higher in energy. This conformer has an interatomic distance of 3.2 {\AA} between the hydrogen atom of the --OH group and the C$=$C bond. The experimentally observed infrared and Raman frequencies agree very well with the calculations and clearly show the presence of these conformers. [Preview Abstract] |
Friday, October 30, 2015 11:21AM - 11:33AM |
C1.00004: Vibrational Spectra, Conformations, and Theoretical Calculations for Cyclohexane, Chlorocyclohexane, Bromocyclohexane and their Isotopomers Hye Jin Chun, Esther Ocola, Jaan Laane The infrared and Raman spectra of cyclohexane and its d$_{\mathrm{11}}$ and d$_{\mathrm{12}}$ isotopomers have been recorded and analyzed. The studies were complemented by \textit{ab initio} (MP2-ccpVTZ) and density functional theory (DFT/B3LYP-ccpVTZ) calculations. The conformational energies of different structures of the molecules were calculated. Vibrational spectra were also recorded for chlorocyclohexane-d$_{\mathrm{0}}$ and -d$_{\mathrm{11}}$ and bromocyclohexane-d$_{\mathrm{0}}$ and -d$_{\mathrm{11}}$. Theoretical computations were also performed to calculate the spectra and molecular conformational energies of the halocyclohexanes. [Preview Abstract] |
Friday, October 30, 2015 11:33AM - 11:45AM |
C1.00005: Rovibrational Energies of H2$+$ Using Fully Nonadiabatic Wavefunctions Steve Alexander, R.L. Coldwell Using variational Monte Carlo methods we examined a number of fully nonadiabatic trial wavefunctions in order to determine which features best describe the lowest several rovibrational states of H$_{\mathrm{2}}^{\mathrm{+}}$ and its isotopormers. We found that vibrational states could be easily described but that rotational excited states are more complicated. We show how the energies produced by these forms compare to previous calculations and discuss how the results of this work can be applied to larger systems. [Preview Abstract] |
Friday, October 30, 2015 11:45AM - 11:57AM |
C1.00006: The effect of isotopic labeling on 4-oxo-TEMPO free radical on $^{13}$C dynamic nuclear polarization Peter Niedbalski, Andhika Kiswandhi, Christopher Parish, Lloyd Lumata Dynamic nuclear polarization (DNP) is a physics technique that amplifies the nuclear magnetic resonance (NMR) signals by transferring the high polarization of the electrons to the nuclear spins. Thus, the choice of free radical is crucial in DNP as it can directly affect the NMR signal enhancement levels, typically on the on the order of several thousand-fold in the liquid-state. In this study, we investigate the efficiency of four variants of the well-known 4-oxo-TEMPO radical (normal 4-oxo-TEMPO plus its $^{15}$N-enriched and/or perdeuterated variants) for use in DNP of an important metabolic tracer [1-$^{\, 13}$C]acetate. Our findings indicate that, despite the differences seen in electron paramagnetic resonance (EPR) spectra, changing the composition of the TEMPO radical through deuteration or $^{15}$N doping yields no significant difference in $^{13}$C DNP efficiency at 3.35 T and 1.2 K. Deuteration of the solvent causes a significant increase of $^{13}$C polarization that is consistent over all the 4-oxo-TEMPO variants. These findings are consistent with the thermal mixing model of DNP. [Preview Abstract] |
Friday, October 30, 2015 11:57AM - 12:09PM |
C1.00007: Real-time spectroscopic detection of yttrium ion and ligand binding via hyperpolarized $^{\mathrm{89}}$Y NMR Sarah Ferguson, Andhika Kiswandhi, Zoltan Kovacs, Lloyd Lumata The physics-based technology fast dissolution dynamic nuclear polarization (DNP) can be used to enhance the signal strength in nuclear magnetic resonance (NMR) and imaging (MRI) experiments for nuclear spins with low gyromagnetic ratio such as yttrium-89. One of the most common and stable MRI contrast agents used in the clinic is Gd-DOTA. In this study, we have investigated the binding of the yttrium and DOTA ligand as a model for complexation of Gd ion and DOTA ligand. The macrocyclic ligand DOTA is special because its complexation with lanthanide ions such as Gd$^{\mathrm{\mathbf{3+}}}$ or Y$^{\mathrm{\mathbf{3+}}}$ is highly pH dependent. Using this physics technology, we have tracked the complexation kinetics of hyperpolarized Y-triflate and DOTA ligand in real-time and detected the Y-DOTA intermediates. Different kinds of buffers were used (lactate, acetate, citrate, oxalate) and the pseudo-first order complexation kinetic calculations will be discussed. [Preview Abstract] |
Friday, October 30, 2015 12:09PM - 12:21PM |
C1.00008: Optimization of 13C dynamic nuclear polarization at 5 Tesla Andhika Kiswandhi, Lama Bimala, Peter Niedbalski, Mudrekh Goderya, Joanna Long, Lloyd Lumata Dissolution dynamic nuclear polarization (DNP) is a physics-based technique that amplifies the magnetic resonance spectroscopy (MRS) and imaging (MRI) signals by several thousand-fold. In this work, we have investigated two optimization methods for preparing $^{13}$C DNP samples (glassing matrix deuteration and Gd$^{3+}$ doping) at B = 5 T. Normally, these optimization methods work favorably at W-band field or 3.35 T. At 5 T, deuteration of the glassing matrix still results in an improvement of the $^{13}$C DNP when 4-oxo-TEMPO free radical is used. This effect can be attributed to the lower heat load of the deuterons than protons. An addition of trace amount of Gd$^{3+}$ is still relatively beneficial in enhancing the polarization when trityl OX063 free radical is used, albeit with a less pronounced improvement compared to the results at B = 3.35 T. This suggests that the signal enhancement due to the addition of Gd$^{3+}$ can become saturated at high field. These results will be discussed using a thermodynamic model of DNP. [Preview Abstract] |
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