A ROTATIONALLY RESOLVED REMPI-PES STUDY OF THE NH RADICAL

The NH radical produced selectively in its a 1-DELTA excited state by photodissociation of HN3 has been investigated by (2 + 1) REMPI-PES in the range 246-286 nm. Vibrational and rotational structure is evident in the photoelectron spectra of all the 3p Rydberg states previously assigned, thereby permitting the determination of accurate values for the first ionization energy. New states further to the blue permit determination of the ionization energy to the next ionic state, A 2-SIGMA-. Wavelength scans for the new g 1-DELTA(upsilon' = 1) <-- a 1-DELTA(upsilon" = 0) transition provided a more precise determination of the spectroscopic constants for the g 1-DELTA(upsilon' = 1) state. The vibrational structure in the kinetic energy scans for this intermediate 3p-pi Rydberg state shows a DELTA-upsilon = 0 propensity, with the resolved rotational structure exhibiting both a DELTA-N = even and odd character. The f 1-PI 3p-sigma Rydberg state also shows the expected Franck-Condon behaviour, but with a predominant DELTA-N = even propensity.