Rotationally resolved photoelectron spectrum of the lowest singlet electronic state of NH2 + and ND2 +: photoionization dynamics and rovibrational energy level structure of the ã+ 1A1 state

Abstract

Fully rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectra of NH2 and ND2 have been recorded in the vicinity of the photoelectron band between 99 500 and 103 500 cm−1. The spectra are dominated by a strong band attributed to the transition. Weaker bands are assigned to transitions to highly excited bending levels of the ground ionic state and to the first symmetric stretching and bending levels of the state. The r 0 structure of the amidogen ion in its lowest singlet (ã+) electronic state was derived from an analysis of the rotational structure (r 0(N−H)=1.051(3) Å. α 0(HNH)=109.2(3)°). A model describing the rotational intensities in the photoelectron spectra of asymmetric top molecules [Willitscsh, S., Hollensteuin, Uand Merkt, F., 2004, J. chem. Phys., 120, 1761] was used to demonstrate that photoionization occurs out of a p orbital on the central N atom and that the photoelectron partial wave composition is dominated by the d component. No perturbations in the rotational structure of the lowest levels of the ã+ state resulting from the Renner–Teller coupling to the state could be detected. The adiabatic ionization energy of the transition was determined to be 100 305.8±0.8cm−1 (12.43633±0.00010eV) in NH2 and 100 366.2±0.9cm−1 (12.443 82±0.000 11eV) in ND2.