Excitation Spectra and Photodissociation Dynamics of the <em>B</em>²<em>П</em> State of the N₂O⁺ Ion

Abstract

N2O + ions in the X 2 Π(0,0,0) ground state were prepared by (3+1) resonance-enhanced multiphoton ionization (REMPI) of jet-cooled N2O molecules at 360.55 nm, and then photoexcited to various vibrational levels in the B 2 Π state over a wavelength range of 243-278 nm, followed by dissociation. The photofragment excitation (PHOFEX) spectrum was recorded by measuring the intensity of NO + ion fragments vs excitation wavelength. The rotational constants and spin-orbit coupling were obtained by fitting the rotational structures of the vibrational bands. Thus, the contributions of highly excited vibronic levels of A 2 Σ + states were distinguished from the other bands, and the original band of B 2 Π state was verified. The series of vibrational bands in the PHOFEX spectrum were assigned to the transition of B 2 Π(v1,v2,v3) ←X 2 Π. The average released kinetic energy of dissociation from the various B 2 Π(v1,v2,v3) ionic states was obtained by fitting the spreading contour of the NO + ion peak in time-of-flight mass spectra. Dissociation mechanisms of N2O + (B 2 Π) were proposed with the aid of the theoretical potential energy surfaces of N2O + ions.