Dynamics of high-n Rydberg states employed in zero kinetic energy-pulsed field ionization spectroscopy via the F-1 Delta(2), D-1 Pi(1), and f(3)Delta(2) Rydberg states of HCl

The intensity anomalies in the spin-orbit and rotational branching ratios in the zero kinetic energy pulsed-field ionization (ZEKE-PFI) spectra via the F (1) Delta(2), D (II1)-I-1, and f (3) Delta(2) Rydberg states of HCl have been studied. In general, the branching ratios are observed to depend on three parameters employed in the pulsed field ionization experiment: (i) the delay time between excitation and ionization; (ii) the magnitude of the bias electric field; and (iii) the magnitude of the applied pulsed electric field. The results can be rationalized on the basis of the increasing number of autoionization decay channels that become available to the high-n Rydberg states as each ionization threshold is surpassed. The delay dependence of the ZEKE-PFI spectra via the F (1) Delta(2) state has been analyzed in more detail by ab initio calculations. These calculations show that the observed spin-orbit branching ratios can be reproduced thereby giving evidence for a nonexponential decay of the high-n Rydberg states (n approximate to 100). (C) 1996 American institute of Physics.