Bulletin of the American Physical Society
42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 56, Number 5
Monday–Friday, June 13–17, 2011; Atlanta, Georgia
Session B5: Molecular Structure and Spectroscopy |
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Chair: Ed Eyler, University of Connecticut Room: A705 |
Tuesday, June 14, 2011 10:30AM - 10:42AM |
B5.00001: Spectroscopy of LiRb molecules and prospects for creating ultracold ground state LiRb molecules Sourav Dutta, Adeel Altaf, John Lorenz, D.S. Elliott, Yong P. Chen We present a spectroscopic study of the $X \quad ^{1}\Sigma ^{+}$ and $B$ $^{1}\Pi $ states of LiRb. LiRb molecules were formed in a heat-pipe oven and spectroscopic measurements of the laser induced fluorescence (LIF) were performed. LIF to the first 45 vibrational levels of the $X \quad ^{1}\Sigma ^{+}$ state (covering more than 98{\%} of the potential well depth) was observed. We also studied the excitation to the $B \quad ^{1}\Pi $ state with high resolution excitation spectroscopy. The values of vibrational, rotational and other spectroscopic constants for both $X \quad ^{1}\Sigma ^{+}$ and $B \quad ^{1}\Pi $ states will be presented in addition to their dissociation energies. Measurements aimed to probe singlet-triplet mixing, as well as perturbations in the $B \quad ^{1}\Pi $ state due to other nearby states will be discussed. The use of such spectroscopic information in finding efficient photoassociation pathways for the production of ultracold LiRb molecules will also be discussed. [Preview Abstract] |
Tuesday, June 14, 2011 10:42AM - 10:54AM |
B5.00002: Long range interactions between like homonuclear alkali metal diatoms Jason Byrd, John Montgomery, Jr., Robin C\^{o}t\'{e} Long range electrostatic and van der Waals coefficients up to terms of order $R^{-8}$ have been evaluated by the sum over states method using {\it ab initio} and time dependent density functional theory. We employ several widely used density functionals and systematically investigate the convergence of the calculated results with basis set size. Static electric moments and polarizabilities up to octupole order are also calculated. We present values for Li${}_2$ through K${}_2$ which are in good agreement with existing values, in addition to new results for Rb$_2$ and Cs$_2$. [Preview Abstract] |
Tuesday, June 14, 2011 10:54AM - 11:06AM |
B5.00003: Blue-detuned photoassociation in Rb$_2$ M.A. Bellos, D. Rahmlow, R. Carollo, J. Banerjee, E.E. Eyler, P.L. Gould, W.C. Stwalley We report on the observation of blue-detuned photoassociation as proposed in [1] and references therein.``Blue-detuned" refers to the location of vibrational levels --- energetically above the corresponding atomic asymptote. $^{85}$Rb atoms in a MOT were photoassociated to levels of the $1\,^3\Pi_g$ state a few hundred wavenumbers above the $5S+5P_{3/2}$ limit. These transitions were found to be strong even though they occur at short internuclear separations ($R_e$=$10\,a_0$). Levels of the $1\,^3\Pi_g$ state were detected by resonantly enhanced multiphoton ionization with time-of-flight spectroscopy (REMPI-TOF). We have observed most vibrational levels of the $1\,^3\Pi_g$ state belonging to all its spin-orbit components ($0_g^+,0_g^-,1_g,2_g$). Some of these levels spontaneously decay preferentially to the $v=0$ level of the $a\,^3\Sigma_u^+$ state (FCF$>0.3$). Therefore in Rb$_2$ it is possible to populate ground ro-vibrational levels of the $a\,^3\Sigma_u^+$ state using just one photoassociation laser.\\[4pt] [1] M.-L. Almazor \emph{et. al.}, Eur. Phys. J. D \textbf{15} 355 (2001). [Preview Abstract] |
Tuesday, June 14, 2011 11:06AM - 11:18AM |
B5.00004: \textit{Ab initio} potential curves for the ground states of Ca$_{2}^+$: Existence of a double minimum in the A$^2 \Sigma_{g}^+$ state Sandipan Banerjee, Jason Byrd, Robin C\^ot\'e, H Michels, John Montgomery We report \textit{ab initio} calculations of the X $^2 \Sigma_{u}^+ $ and A $^2 \Sigma_{g}^+$ states of the Ca$_{2}^+$ dimer. Valence multireference configuration interaction (MRCI) calculations were performed using complete active space self consistent field (CASSCF) orbitals. The CASSCF calculations included all configurations with 3 electrons in 18 valence orbitals and used the aug-cc-pV5Z basis. Core-valence and scalar relativistic effects are included at the CCSDT/cc-pWCVTZ-DK level of theory. A double well, similar to that obtained in recent calculations\footnote{S. Banerjee \textit{et al.} Chem. Phys. Lett. 496 (2010) 208.} on Be$_2^+$ is found in the A $^2 \Sigma_{g}^+$ state. Spectroscopic constants and bound vibrational levels for both the ground states are calculated, as well as Frank-Condon factors and electronic dipole transition moment between the X $^2 \Sigma_{u}^+ $ and A $^2 \Sigma_{g}^+$ states. The static dipole and quadrupole polarizabilities, along with $C_{6}$ dispersion coefficient are also reported. [Preview Abstract] |
Tuesday, June 14, 2011 11:18AM - 11:30AM |
B5.00005: Dissociation Energy of the Ground State of NaH Thou-Jen Whang, Hsien-Yu Huang, Tsai-Lien Lu, Yung-Yung Chang, Chin-Chun Tsai The dissociation energy of the ground state of NaH has been determined by analyzing the observed near dissociation rovibrational levels of X$^1\Sigma^+$ and C$^1\Sigma^+$ states. These levels are carried out by stimulated emission pumping and fluorescence depletion spectroscopy. The highest vibrational level observed in ground state is only about 40\,cm$^{-1}$ from its dissociation limit and is about 30\,cm$^{-1}$ from its dissociation limit for C$^1\Sigma^+$ state. Determining the vibrational quantum number at dissociation $v_D$ from the highest four vibrational levels of ground state yields the dissociation energy $D_e$=15\,815$\,\pm\,$5\,cm$^{-1}$. A Hybrid potential based on the rotationless Rydberg-Klein-Rees curve and the modified \emph{ab} initio calculation is constructed for the C$^1\Sigma^+$ state. The dissociation energy of ground state can be deduced from the asymptotic limit of C$^1\Sigma^+$ state and it agrees well with obtained from the ground state $v_D$. [Preview Abstract] |
Tuesday, June 14, 2011 11:30AM - 11:42AM |
B5.00006: Rydberg states of triatomic hydrogen and deuterium Jia Wang, Chris Greene, Richard Saykally Triatomic hydrogen ($\rm{H_3}$) and its isotopologue ($\rm{D_3} $) are the simplest neutral polyatomic molecules. They have been of great interest in recent decades. In a previous study [1], we calculated radiative transitions between neutral $\rm {H_3}$ Rydberg states and described the mid-infrared laser lines observed in hydrogen/rare gas discharges. We extend the study to $\rm{D_3}$, and discuss the mechanism for the population inversion that is required for lasing action, which has been observed by the Berkeley group.\\[4pt] [1] R. J. Saykally, E. A. Michael, J. Wang, and Chris H. Greene, J. Chem. Phys. \textbf{133}, 234302 (2010). [Preview Abstract] |
Tuesday, June 14, 2011 11:42AM - 11:54AM |
B5.00007: Partial derivatives of eigenvalues without finite differences J.F. Babb Partial derivatives of eigenvalues and eigenvectors with respect to parameters appear widely in descriptions of collisional and spectroscopic phenomena. Usually finite difference methods are employed for evaluations but they are sometimes inefficient or unstable. There are, however, several algorithms that can yield partial derivatives by iterative solution of matrix equations. The methods do not appear to be widely used in atomic and molecular physics. The algorithms will be described in this paper and results of tests on model problems and on the hydrogen molecular ion will be presented. [Preview Abstract] |
Tuesday, June 14, 2011 11:54AM - 12:06PM |
B5.00008: Frequency-Comb Velocity-Modulation Spectroscopy Laura Sinclair, Kevin Cossel, Tyler Coffey, Jun Ye, Eric Cornell We have developed a novel technique for broad spectral bandwidth rapid ion-sensitive spectroscopy. This technique combines the high sensitivity of velocity-modulation spectroscopy with the parallel nature and high frequency accuracy of cavity-enhanced direct frequency comb spectroscopy. Prior to this research, no techniques have been capable of high sensitivity velocity modulation spectroscopy on every parallel detection channel over such a broad spectral range. We have demonstrated the power of this technique by measuring the $A^{2}\Pi_{u} - X^{2}\Sigma^{+}_{g}$ (4,2) band of N$^{+}_{2}$ with an absorption sensitivity of $10^{-6}$ for each of 1500 simultaneous measurement channels spanning 150 cm$^{-1}$. A fully sampled spectrum with 75 MHz spacing consisting of interleaved measurements is acquired in under an hour. Currently, this technique is being used to map the electronic transitions of HfF$^{+}$ for the JILA electron electric dipole moment experiment. This work was funded by the NSF. [Preview Abstract] |
Tuesday, June 14, 2011 12:06PM - 12:18PM |
B5.00009: Collisional Orientation Transfer Facilitated Polarization Spectroscopy J. Bai, E. Ahmed, B. Beser, Y. Guan, M. Lyyra, S. Ashman, C. Wolfe, J. Huennekens We report extensive collisional orientation transfer in V-type double-resonance polarization spectroscopy of the A$^{1}\Sigma _{u}^{+} \quad \sim $ b$^{3}\Pi _{u}$ complex of Rb$_{2 }$and Cs$_{2}$. Using this technique, in the Cs$_{2}$ case, we were able to observe a gap region in the A$\sim $b complex with poor Franck Condon factors (FCF) with the ground state. Since spectral congestion makes it difficult to find isolated pump transitions for a heavy molecule such as Cs$_{2}$, this technique allows us to observe many more rotational levels for each vibrational level than the customary strong $\Delta $J= $\pm $ 1 transitions. For probe transitions with very small FCF values we were able to observe angular momentum change with $\Delta $J$_{max}$ = 12, while in an analogous study of the Rb$_{2}$ A $\sim $ b complex of states, for transitions with larger FCF values, the maximum observed angular momentum change of the collisional satellite lines was $\Delta $J$_{max}$ = 58. Although collisional satellites lines were observed in polarization spectroscopy previously at a much higher pressure of several hundred Torr, our experiments were done at 1 Torr pressure without any loss in resolution. [Preview Abstract] |
Tuesday, June 14, 2011 12:18PM - 12:30PM |
B5.00010: Dual channel system for two-photon excited fluorescence-based relative measurements of high accuracy two-photon absorption spectra Nikolay Makarov, Joel Hales, Joseph Perry We describe an experimental setup for reliable relative measurements of two-photon absorption spectra of organic molecules. The set-up utilizes tunable femtosecond laser system with optical parametric amplifier (OPA) and covers excitation wavelengths in the range 550-1600 nm. It utilizes two channels for simultaneous measurements of the unknown sample and the reference, such that all the pulse-to-pulse laser instabilities cancel out during measurements. Using the setup we measure absolute two-photon absorption (2PA) spectra of 4 commercial organic dyes (Rhodamine 640, Rhodamine 700, LDS-698 and LDS-798) with an estimated accuracy 15{\%}. The data are corrected for the variations of the pulse duration and the beam profile with the excitation wavelength, and are applicable as secondary reference standards for 2PA measurements of the compounds with the emission wavelengths 600-800 nm. [Preview Abstract] |
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