Rotationally resolved photoelectron spectrum of the lowest singlet electronic state of NH2+ and ND2+:: photoionization dynamics and rovibrational energy level structure of the (a)over-tilde+ 1A1 state

Fully rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectra of NH2 and ND2 have been recorded in the vicinity of the (X) over tilde B-2(1) --> (a) over tilde (+) (1)A(1) photoelectron band between 99 500 and 103 500 cm(-1). The spectra are dominated by a strong band attributed to the (X) over tilde B-2(1) (0, 0, 0) --> (a) over tilde+ (1)A(1) (0, 0, 0) transition. Weaker bands are assigned to transitions to highly excited bending levels of the (X) over tilde (+) B-3(1) ground ionic state and to the first symmetric stretching and bending levels of the (a) over tilde (+) state. The r(o) structure of the amidogen ion in its lowest singlet ((a) over tilde (+)) electronic state was derived from an analysis of the rotational structure (r(o)(N-H) = 1.051(3) Angstrom, alpha(o)(HNH) = 109.2(3)degrees). A model describing the rotational intensities in the photoelectron spectra of asymmetric top molecules [WILLITSCH, S., HOLLENSTEIN, U., and 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 (a) over bar (+) state resulting from the Renner-Teller coupling to the (b) over tilde (+) state could be detected. The adiabatic ionization energy of the (X) over tilde --> (a) over tilde (+) transition was determined to be 100 305.8 +/- 0.8 cm(-1) (12.43633 +/- 0.000 10 eV) in NH2 and 100 366.2 +/- 0.9 cm(-1) (12.443 82 +/- 0.000 11 eV) in ND2.