THE DYNAMICS OF PREDISSOCIATING HIGH RYDBERG STATES OF NO

In this paper we present a theoretical study of the predissociation dy namics of the nf(N+ = 2) (with the principal quantum numbers n=40-95) and the np(N+=0) (n=70-125) Rydbrg series of NO, which exhibit a marke d lifetime dilution (lengthening) at n > 65 for the f series and at n > 116 for the p series [M.J.J. Vrakking and Y. T. Lee, J. Chem. Phys. 102, 8818 (1995)]. The multichannel effective Hamiltonian with several doorway (for excitation) and escape (for decay) states was constructe d using experimental information on the quantum defects and on the dec ay width constants incorporating both intramolecular coupling and exte rior electric field coupling between high Rydbergs. The analysis of th e intramolecular Rydberg electron-core dipole long range coupling (H-R -D) in conjunction with the energy gaps between proximal pairs of ener gy levels, which are subjected to appropriate selection rules, reveals that (i) for low l(less than or equal to 3) core-penetrating Rydbergs only a small number of accidental near-resonances are exhibited, and (ii) for high l(>3) nonpenetrating Rydbergs the electron-core dipole c oupling decreases fast with increasing l, i.e., (H-R-D)proportional to l(-7). The general characteristics of the high l(>3) manifold establi sh a bottleneck effect, which precludes intramolecular l mixing, imply ing that high Rydberg lifetime dilution effects can be induced only by exterior electric field coupling (H-STARK). Parameter-free multichann el effective Hamiltonian calculations were conducted under narrow-band excitation conditions, which interrogate the electric field induced m ixing in the energetic vicinity of the doorway state. The electric fie ld induced l mixing model accounts semiquantitatively for the electric field dependence of the energy-resolved line shapes of the nf(N+=2) s eries and for the n and electric field dependence of the lifetimes of the nf(N+=2) and the np(N+=0) series. Accidental near-resonant simulta neous intramolecular and electric held coupling [GRAPHICS] for two set s of proximal states n=92, n'=80 and n=95, n'=82, result in mediated-s equential mixing, which is manifested by slow decay times below the on set of effective electric field mixing by weak (F-0 similar or equal t o 0.04-0.08 V/cm) stray electric fields. (C) 1996 American Institute o f Physics.