Angular distributions of photoelectrons from resonant two-photon ionization of sodium through the3p0P322intermediate state

Abstract

Angular distributions of photoelectrons from resonant two-photon ionization of sodium have been measured. Excitation and ionization were carried out with two pulsed lasers, one with a frequency resonant with the $3s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\to 3p{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ transition. The hyperfine levels in the intermediate state were excited coherently; hyperfine coupling affects the photoelectron distributions through a dependence on the time interval between excitation and ionization. The results are analyzed to give values of three microscopic parameters: the ratio of the radial dipole matrix elements for the production of $l=0\mathrm{}$ and $l=2\mathrm{}$ final states from the $3p$ level, the difference of the phase shifts of the outgoing electron in the final channels, and a parameter which expresses the depolarizing effect of the nuclear spin on the intermediate state. The phase-shift difference agrees with extrapolated bound-state data, but the final state has more $s$ character than theoretical quantum-defect calculations suggest.