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The Journal of Physical Chemistry

The LiHg(22Π3/2− ) System

Dieter Gruber, X. Li, Laurentius Windholz, Matthias M. Gleichmann, B.A. Hess, Igor Vezmar, Goran Pichler

Published Jan 1, 1996• 8 citations
Publisher

Abstract

We report the determination of the complete LiHg shallow bound ground state potential curve by combination of laser-induced fluorescence spectroscopy of bound−bound transitions, photoassociation spectroscopy of bound−free transitions, and ab initio calculations. The results are evaluated by comparison of quantum mechanically simulated emission spectra with experimental data and used to describe spectroscopic features of the 2 2 Π 3/2 − band as well as the photochemical formation via excitation of the lithium dimer.

DOI
10.1021/jp9602078

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•Jan 1, 2014•1 citation
We report the determination of the complete LiHg shallow bound ground state potential curve by combination of laser-induced fluorescence spectroscopy of bound−bound transitions, photoassociation spectroscopy of bound−free transitions, and ab initio calculations. The results are evaluated by comparison of quantum mechanically simulated emission spectra with experimental data and used to describe spectroscopic features of the 2 2 Π 3/2 − band as well as the photochemical formation via excitation of the lithium dimer.
We report the first observation of laser-induced fluorescence of the CsHg molecule. Cs/Hg vapor mixtures contained in a heat-pipe oven were excited by several different argon ion laser lines. Following these excitations, we observed three distinct peaks at λ=492.8, λ=498.3, and λ=521.5 nm in addition to the well-known fluorescence of the Cs2 molecule. Based on an analysis using ab initio potential energy curves of Cs2 and CsHg, we identified the origin of these three distinct peaks as bound–free transitions of CsHg (λ=492.8: IV3/2→X1/2, λ=498.3: VII1/2→X1/2, and λ=521.5 nm: VI1/2→X1/2). Furthermore, we could show that two different production channels are responsible for the formation of the CsHg molecules in the excited states. The excitation of the Cs/Hg vapor mixtures with wavelengths λexc=476–514 nm of the argon ion laser results in the production of the CsHg molecules via a photoassociation process, whereas the CsHg molecules are produced in a three-body collision following an excitation with λexc=457 nm. These results are confirmed by subsequent quantum-mechanical simulations of the observed laser-induced fluorescence spectra of CsHg.
We present an accurate potential energy curve of the B (1)Pi state in the LiCs molecule for which vibrational levels between v(') = 0 and v(') = 35 (bound by 11.4 GHz) were measured by photoassociation spectroscopy in an ultracold ensemble of (7)Li and (133)Cs atoms. By the combination of conventional spectroscopic data of the B-X system and the new photoassociation measurements a very precise value of the dissociation energy of the ground state X (1)Sigma(+) of LiCs was determined to be D(0) = 5783.495(5) cm(-1).
We report observations and analysis of the laser-excited photoluminescence of Sr2. The spectra contains some discrete molecular line spectra, but is dominated by extensive, deeply modulated continua characteristic of bound–free transitions of excimer systems. Dye laser and argon laser excitation of the Sr2 dimer is used. Some of the spectra is attributed to fluorescence from dimers created by laser induced photoassociation of free Sr atoms. Techniques are developed to obtain Morse potential parameters by computer modeling of the observed spectra. We find for the X 1Σ+g state, De=1100±100 cm−1, ωe=39.6±1 cm−1; for the A 1Σ+u state, De=5460±100 cm−1, ωe=83±3 cm−1; and Re″−Re′=0.49±0.02 Å. Strong collision-induced predissociation is observed and attributed to a potential curve crossing. Cross sections for dissociation by argon are reported as a function of laser excitation wavelength.
Abstract The electronic structure and the spectroscopic properties for low‐lying electronic states of the LiRb+ molecular ion, dissociating into Li (2s, 2p, 3s, 3p, 3d, 4s, and 4p) + Rb+ and Li+ + Rb (5s, 5p, 4d, 6s, 6p, 5d, and 7s), have been investigated using an ab initio approach based on non‐empirical pseudo potentials for the Li and Rb cores and parametrized l‐dependent polarization potential. We have determined the adiabatic potential energy curves and their spectroscopic constants for many electronic states of 2Σ+, 2Π, and 2Δ symmetries. A satisfying agreement, for the spectroscopic constants, has been obtained for the ground and the first excited states with the available theoretical works. Potential energy curves were presented, for the first time, for the higher excited states. In addition, we have localised and analysed the avoided crossings between electronic states of 2Σ+ and 2Π symmetries. Their existences can be related to the interaction between the potential energy curves and to the charge transfer process between the two ionic systems Li+Rb and LiRb+. Moreover, we have determined the transition dipole moments from X2Σ+ and 22Σ+ states to higher excited states of 2Σ+ and 2Π symmetries. For our best knowledge, no experimental data on the LiRb+ molecular ion is available. These theoretical data can help experimentalists to optimize photoassociative formation of ultracold LiRb+ molecular ion and their longevity in a trap or in an optical lattice. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
We have obtained high-lying vibrational spectra for the rm1sp3Sigmasbspg+\\rm 1\\sp3\\Sigma\\sbsp{g}{+}rm1sp3Sigmasbspg+ and rm1sp1Sigmasbspu+\\rm 1\\sp1\\Sigma\\sbsp{u}{+}rm1sp1Sigmasbspu+ excited states of both rmsp7Lisb2\\rm \\sp7Li\\sb2rmsp7Lisb2 and rmsp6Lisb2\\rm \\sp6Li\\sb2rmsp6Lisb2 via photoassociation of colliding ultracold lithium atoms confined in a magneto-optical trap. Photoassociative spectroscopy of ultracold atoms is a powerful tool for probing molecular states near the dissociation energy that are inaccessible by other methods. For an ultracold lithium vapor, the distribution of unbound ground state energies is so small that precise free-bound spectroscopy is possible. Molecular hyperfine structure is resolved. We calculate accurate dissociation energies for both the rm1sp3Sigmasbspg+\\rm 1\\sp3\\Sigma\\sbsp{g}{+}rm1sp3Sigmasbspg+ and rm1sp1Sigmasbspu+\\rm 1\\sp1\\Sigma\\sbsp{u}{+}rm1sp1Sigmasbspu+ excited states of Lisb2\\sb2sb2. A model potential is constructed from a combination of experimental and theoretical information, and used to assign vibrational quantum numbers. We observe rotational structure and assign rotational quantum numbers.
We present the results of a spectroscopic study LiRb molecules created via photoassociation (PA) to vibration levels of the 4(1) potential. Atoms are first cooled and trapped in a dual species 7Li/ 85Rb magneto-optical trap (MOT) at temperatures of ≈ 1 mK or less. In a cold sample of sufficient density, PA occurs when a resonant laser field induces a free-bound transition to create molecules in an excited electronic potential. After spontaneous emission the molecules decay to a mixture of free atoms and bound molecules depending on the Franck-Condon factors (FCFs) of the excited and ground state vibrational wavefunctions. While excited LiRb * has been previously detected by trap loss fluorescence detection, ionization spectroscopy is required to determine the population of ground state levels after decay. We detect ground state molecules via resonantly enhanced multiphoton ionization (REMPI) where a two photon ionization transition is enhanced by an intermediate resonance. The intermediate resonances match progressions from the D1Π and possibly B1&Pgr; potentials, many of which have known energies obtained from previous heat pipe experiments. This is contrary to the expectation that weakly bound LiRb * should primarily decay to weakly bound levels of the ground state and could point to a possible path for creating molecules in the rovibronic ground state.