CORRECTIONS TO AB INITIO CESIUM-ARGON INTERACTION POTENTIALS DETERMINED BY SIMULATION OF FREE→FREE ABSORPTION SPECTRA Darby Hewitt, Thomas Spinka, Jason Readle, and Gary Eden Laboratory for Optical Physics and Engineering University of Illinois at Urbana-Champaign June 17, 2013 1

Motivation Numerous ab initio calculations have been performed for the Cs-Ar system to determine pair interaction potentials (Baylis [1969], Pascale [1974], Dhiflaoui [2010], Blank [2012]) Calculated XΣ and BΣ potentials share similar qualitative features, but simulated absorption spectra based on these states inaccurately predict spectral position of the blue satellite of the D2 transition Ab initio interaction potentials can be improved by iterative adjustment and comparison between simulated and experimental spectra These modified potentials can more accurately represent gas-phase dynamics of excited alkali-rare gas pairs Add diode array beam quality? Narrower linewidth desired?

B2Σ States of Cs-Ar in the Literature

Simulated Spectra from ab initio Potentials

Four Regions Of B State

Spectral Simulation Considerations Ground-state interaction potential accounts for scattering data found in literature (Malerich et al., 1976) and long-range dispersion interaction (Cvetko et al., 1994) Wavefunctions calculated using Numerov-Cooley method (1961), normalized according to energy above dissociation asymptote (Buckingham, 1961) Energy range truncated at 8kT

Energy Range for Wavefunction Calculation Truncation of rotational states performed using collisional impact parameter according to: Where E is energy of the pair in the ground state For the purposes of this simulation, b is defined as the innermost R value where the magnitude of the first derivative of the XΣ potential ≤2 cm-1/Å Energy range: 0-8kT, ~90% of all states

Franck-Condon Factors J = 40

Results

Potential Curve Comparison

Summary Simulation demonstrates the sensitivity of absorption spectra to minor changes in interaction potentials Comparison between simulation and data provides means to make informed corrections to the B state for alkali-rare gas pairs Simulation with modified BΣ potential based on ab initio potentials for Cs-Ar exhibits better agreement with experimental absorption spectrum

References W. E. Baylis J. Chem. Phys. 51, 2665 (1969) J. Pascale and J. Vandeplanque J. Chem. Phys. 60, 2278 (1974) J. Dhiflaoui and H. Berriche J. Phys. Chem. A 114, 7139 (2010) L. Blank, David E. Weeks, and Gary S. Kedziora J. Chem. Phys. 136, 124315 (2012) C. J. Malerich, K. B. Povodator, and R. James Cross Jr. Chem. Phys. 20, 409 (1977) D. Cvetko, A. Lausi, A. Morgante, F. Tommasini, P. Cortona, and M. G. Dondi J. Chem. Phys. 100, 2052 (1994) J. W. Cooley Math. Comp. 15, 363 (1961)