Infrared Spectroscopy of Highly Excited Vibrational Levels of Protonated Nitrogen, HN +2

Abstract

A difference frequency laser spectrometer along with velocity modulation was used to record the absorption spectrum of molecular ions produced in a glow discharge with a gas mixture of N 2/H 2/He in a ratio around 1/1/100. Thirty-two new hot bands of HN + 2 associated with the ν 1 fundamental hand have been observed and analyzed in the spectral region between 2900 and 3500 cm −1. Molecular constants have been determined by litting each observed band toa simple standard power series expansion as well as by using a simultaneous least-squares fit of all the observed bands. The determined molecular constants are believed to be the most complete and accurate available today. Some perturbations and high anharmonicity effects have been revealed. The determined vibrational temperatures associated with the ν 1, ν 2, and ν 3 modes are 4000, 1550, and 3100 K (±10%), respectively. These values, much higher than the evaluated rotational temperature, i.e., 400 K (±10%), reflect our observation of highly excited vibrational levels of HN + 2 ion. Some hypotheses on the ion formation and on the relaxation and excitation processes occurring in our discharge are used to comment upon this observation.