Complete determination of atomic parameters in two -photon ionization and study of quantum interference with two -color laser fields

We present our study on complete measurements of two-photon ionization in atomic rubidium. In this study we developed an effective technique to measure the angular distributions of photoelectrons. Through the measurements with this technique and using elliptically-polarized light we have successfully determined the atomic parameters—the relative cross sections for various ionization channels as well as the phase difference between s- and d-continuum waves. The measured phase differences are in excellent agreement with expected values over the entire range of photoelectron kinetic energy from 0 to 0.5 eV. The measured relative cross sections for ionization into S and D channels are also in good agreement with theoretical data. Both the relative cross sections and phase differences show a slow variation as a function of photoelectron energy. The ratios of cross sections of the two D channels are not in agreement with the expected value, suggesting fine structure effects. We also studied a quantum mechanical interference using two-color laser fields and observed the extremely asymmetric photoelectron angular distribution produced by interfering even- and odd-order photoionization processes in atomic rubidium as the optical phase was varied. We observed these effects with both perpendicularly and parallel-polarized fields components. It is worthy to note that the quantum interference observed with perpendicularly-polarized two-color fields is unique. Based on the analysis of measured angular distributions we derived the phase difference between even and odd continuum waves for the first time. The measured value of the phase difference is in good agreement with the calculated value from quantum defect theory