SINGLE-PHOTON THRESHOLD PHOTOIONIZATION OF NO

Single-photon threshold photoionization spectra for jet-cooled NO have been measured for the v+ = 0 and 1 vibrational levels of the X 1SIGMA + ground state of NO+. The NO+ rotational state distribution for the v + = 0 level is shown to be perturbed by nearby autoionizing levels, wh ereas the v+ = 1 level exhibits a cation rotational distribution which is in near quantitative agreement with calculated spectra near thresh old. Only small changes in total angular momentum are observed (\DELTA J\ = \J+ -J''\ less-than-or-equal-to 5/2) even though a wide range of photoelectron angular momenta (l = 0-3) are predicted to contribute to the near-threshold photoelectron continua. The present results are al so discussed in light of recently published two-photon threshold photo ionization spectra of NO which exhibit nearly identical NO+ rotational state distributions.