Bulletin of the American Physical Society
81st Annual Meeting of the APS Southeastern Section
Volume 59, Number 18
Wednesday–Saturday, November 12–15, 2014; Columbia, South Carolina
Session CC: Atomic, Molecular and Optical Physics I |
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Chair: John Yukich, Davidson College Room: Richland II |
Thursday, November 13, 2014 11:00AM - 11:36AM |
CC.00001: Precision Atomic Mass for Neutrino Mass Invited Speaker: Edmund Myers Observations of neutrino oscillations have shown that neutrinos can exist in three mass eigenstates and have produced values for the differences in the squares of their masses. However, the absolute masses are still unknown. One laboratory method for obtaining an upper limit to (and possibly measuring) electron-neutrino mass is to study the energy spectrum of the electrons emitted in a low-energy beta-decay near its endpoint. This approach is being pursued with the large-scale tritium-beta-decay experiment KATRIN, which should reduce the upper limit on electron-neutrino mass to below 0.2 eV. As an alternative approach, if it is assumed that neutrinos are Majorana particles, information on absolute neutrino mass can be obtained from the rate of neutrino-less double-beta decay, a process which has yet to be conclusively observed. In both approaches, an independent value for the beta-decay Q-value, as obtained from the mass difference between the parent and daughter atoms, is important in validating the neutrino mass limit obtained. After discussing this motivation, we will explain how we measure atomic masses to better than 0.1 parts-per-billion fractional precision using single ions in a Penning ion trap. We will also present our new result for the mass difference between tritium and helium-3, which has an estimated uncertainty below 0.1 eV. [Preview Abstract] |
Thursday, November 13, 2014 11:36AM - 12:12PM |
CC.00002: Full-dimensional quantum dynamics calculations of rovibrationally inelastic scattering of CO-H$_2$ Invited Speaker: Benhui Yang The CO-H$_2$ collisional system is crucial in determining the physics and chemistry of interstellar environments due to the astrophysical importance of H$_2$ and CO. We calculated for the first time a full-dimensional (6D) potential energy surface (PES) for this system using the high-level CCSD(T)-F12B method. The PES was fitted using an invariant polynomial method in 6D. Quantum close-coupling calculations of rotational and vibrational quenching of CO in collisions with H$_2$ were carried out on the new 6D PES. The pure state-to-state rotational excitations from CO($v_1=0$, $j_1$=0, 1) were benchmarked with crossed molecular beam measurement for collision energies of 795 - 991 cm$^{-1}$ and 3.3 - 22.5 cm$^{-1}$. The computed cross sections for $j_1=0 \rightarrow 1$ transition in CO and show better agreement with measurement than those obtained on a recently available 4D PES. For rovibrational transitions, state-to-state and total quenching cross sections and rate coefficients were calculated for the vibrational quenching in CO($v_1=1, j_1$)+H$_2$($v_2=0, j_2$) $\rightarrow$ CO($v_1^{\prime}=0, j_1^{\prime}$)+H$_2$($v_2^{\prime}=0, j_2^{\prime}$) collisions, $j_1=0, 2$ for para-H$_2$ and $j_1=1, 3$ for ortho-H$_2$. The results are compared with experimental results and previous calculations using 4D PESs and various decoupling approximations. Our calculation also confirmed that the contribution from a quasi-resonant channel, CO($v_1$=1) + H$_2$($v_2$=0, $j_2$=2) $\rightarrow$ CO($v_1^{\prime}$=0) + H$_2$($v_2^{\prime}=0$, $j_2^{\prime}$=6), dominates the vibrational quenching of CO in collision with para-H$_2$ for $T\geq 50$~K. [Preview Abstract] |
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