Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session K02: Advances in Spectroscopy of the Hydrogen Molecule, Its Isotopologues, and Its Ion |
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Sponsoring Units: GPMFC Chair: David Hanneke, Amherst College Room: Wisconsin Center 101AB |
Wednesday, May 29, 2019 2:00PM - 2:30PM |
K02.00001: Physics beyond the Standard Model from hydrogen molecules Invited Speaker: Wim Ubachs The hydrogen molecule is the smallest neutral chemical entity and a benchmark system of molecular spectroscopy. The comparison between highly accurate measurements of transition frequencies and level energies with quantum calculations including all known phenomena (relativistic, vacuum polarization and self-energy) provides a tool to search for physical phenomena in the realm of the unknown: are there forces beyond the three included in the Standard Model of physics plus gravity, are there extra dimensions beyond the 3$+$1 describing space time? Comparison of laboratory wavelengths of transitions in hydrogen may be compared with the lines observed during the epoch of the early Universe to verify whether fundamental constants of Nature have varied over cosmological time. These concepts, as well as the precision laboratory experiments and the astronomical observations used for such searches of new physics will be discussed. [Preview Abstract] |
Wednesday, May 29, 2019 2:30PM - 3:00PM |
K02.00002: Molecules in intense laser fields: Ultrafast dynamics and high-resolution spectroscopy Invited Speaker: Kaoru Yamanouchi By pump-probe measurements with high temporal resolution using near-IR few-cycle laser pulses, we revealed that the yield of H$_{\mathrm{3}}^{\mathrm{+}}$ generated from CH$_{\mathrm{3}}$OH$^{\mathrm{2+}}$ exhibits a long-lasting periodic increase reflecting the motion of the vibrational wave packet in methanol cation along the C-O bond stretching coordinate, showing that the time-resolved measurement of the yields of fragment ions is an efficient tool not only for probing ultrafast nuclear dynamics of molecular cations but also for deriving their vibrational frequencies. We further performed pump-probe measurements of methanol and its isotopologues (CH$_{\mathrm{3}}$OH, CH$_{\mathrm{3}}$OD and CD$_{\mathrm{3}}$OH), and obtained the vibrational mode frequencies of methanol and methanol cations by Fourier transform (FT) of the yields of the parent ion and the fragment ions recorded as a function of the pump-probe delay time. In order to examine how high the resolution of a frequency domain spectrum obtained by strong field FT spectroscopy could be, we performed pump-probe measurements of the yields of D$_{\mathrm{2}}^{\mathrm{+}}$ and D$^{\mathrm{+}}$ produced after the photoionization of D$_{\mathrm{2}}$ using intense near-IR few-cycle laser pulses. The yields of D$_{\mathrm{2}}^{\mathrm{+}}$ and D$^{\mathrm{+}}$ recorded up to the pump-probe delay time of 527 ps exhibited oscillatory structures reflecting the motion of the created vibrational wave packet of D$_{\mathrm{2}}^{\mathrm{+}}$, and the FT of the data in time domain revealed that the vibrational level separations can be determined with high precision, showing a potential application of the strong-field pump-probe measurements to high-resolution spectroscopy of molecular ions. [Preview Abstract] |
Wednesday, May 29, 2019 3:00PM - 3:30PM |
K02.00003: Quantum Electrodynamics of the hydrogen molecule Invited Speaker: Mariusz Puchalski In 1947 Hans Bethe\footnote{H. Bethe, Phys. Rev. \textbf{72}, 339 (1947)} explained apparent discrepancy between Dirac theory for the hydrogen atom and the measurement of the $2S_{1/2} - 2P_{1/2}$ transition by W. Lamb and R. Retherford. His explanation set the grounds for the development of the quantum electrodynamic theory (QED) by S. Tomonaga, J. Schwinger, R. Feynman and F. Dyson. Inspired by this original work of Bethe, we search for discrepancies between highly accurate spectroscopic measurements for the hydrogen molecule\footnote{N. H\"olsch {\em et al.}, Phys. Rev. Lett. \emph{in print}, (2019)} and theoretical predictions\footnote{M. Puchalski, J. Komasa, and K. Pachucki, Phys. Rev. Lett. \textbf{120}, 083001 (2018)} \footnote{M. Puchalski, J. Komasa, P. Czachorowski, and K. Pachucki, Phys. Rev. Lett. \emph{in print}, (2019)} based on QED, in order to discover new effects or even new interactions which might result in the developement of Standard Model of fundamental interactions. [Preview Abstract] |
Wednesday, May 29, 2019 3:30PM - 4:00PM |
K02.00004: Cavity-enhanced Lamb-dip spectroscopy of HD at 1.39 $\mu$m with $10^{-10}$ precision Invited Speaker: Shui-Ming Hu Energy levels in the electronic ground state of the hydrogen molecule can be calculated precisely based on quantum electrodynamics (QED) and a few fundamental physical constants. Therefore, precision spectroscopy of H$_2$ (and its isotopologues) is a test ground of QED and may serve for determination of those constants. Recent progress shows that the accuracy of calculation is approaching the level of sub-MHz [Puchalski et al., PRL 2018, 121:073001]. However, high-precision measurements of the ro-vibrational spectroscopy of the hydrogen molecule is very difficult due to extremely weak transition moments. Recently, two of the very sensitive laser spectroscopy methods both utilizing the sensitivity enhancement from high-finesse cavities, cavity ring-down spectroscopy (CRDS) % cavity enhanced absorption spectroscopy (CEAS), and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS), have been applied to detect the Doppler-free Lamb dips of the lines in the first overtone band ($V=2-0$) of HD at 1.39~$\mu$m. However, the R(1) line centre given by CRDS [Tao et al., PRL 2018, 120:153001] differs from that by NICE-OHMS [Cozijn et al., PRL 2018, 120:153002] by 0.9~MHz which is about 8 times of the combined uncertainty. In this talk, we will review the methods and present our recent experimental progress. We developed an instrument realizing three different cavity-enhanced spectroscopy methods - CRDS, NICE-OHMS, and cavity enhanced absorption spectroscopy (CEAS). Owing to a considerably improved sensitivity, we revealed the reason of the discrepancy observed in previous measurements: The Lamb-dip line of HD has a very unique dispersion-like feature. So far as we know, such profile has not been observed before in other molecules. The line profile was confirmed by all three methods, CRDS, CEAS, and NICE-OHMS, and also by the comparison to the spectra of a nearby C$_2$H$_2$ line observed at same experimental conditions. The weighted centers of the HD line determined from three methods, agreed with each other within a few tens kHz . Provided that the theoretical analysis can also achieve the similar accuracy, the result would lead to a new determination of the proton-to-electron mass ratio at the $10^{-10}$ level. [Preview Abstract] |
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