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arXiv · 0906.1638

One- and two-photon ionization cross sections of the laser excited 6s6p^1P_1 state of barium

John R. Tolsma·Daniel J. Haxton·Rekishu Yamazaki·Daniel S. Elliott·Chris H. Greene
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Abstract

Stimulated by a recent measurement of coherent control in photoionization of atomic barium, we have calculated one- and two-photon ionization cross sections of the aligned 6s6p^1P_1 state of barium in the energy range between the 5d_{3/2} and 5d_{5/2} states of Ba^+. We have also measured these photionization spectra in the same energy region, driving the one- or two-photon processes with the second or first harmonic of a tunable dye laser, respectively. Our calculations employ the eigenchannel R-matrix method and multichannel quantum defect theory to calculate the rich array of autoionizing resonances in this energy range. The non-resonant two-photon process is described using lowest-order perturbation theory for the photon-atom interactions, with a discretized intermediate state one-electron continuum. The calculations provide an absolute normalization for the experiment, and they accurately reproduce the rich resonance structures in both the one and two-photon cross sections, and confirm other aspects of experimental observations. These results demonstrate the ability of these computationally inexpensive methods to reproduce the experimental observables in one- and two-photon ionization of heavy alkaline earths, and they lay the groundwork for future studies of the phase-controlled interference between one-photon and two-photon ionization processes.

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John R. Tolsma, Daniel J. Haxton, Rekishu Yamazaki, Daniel S. Elliott, Chris H. Greene. 2009-06-09. One- and two-photon ionization cross sections of the laser excited 6s6p^1P_1 state of barium. https://doi.org/10.1103/physreva.80.033401

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