High-resolution Fourier spectrometry of 14N 2 and 15N 2 infrared emission spectrum: Extensive analysis of the W3Δ u - B3Π g system

Abstract

The infrared spectrum of the nitrogen molecule, excited in a microwave discharge, has been recorded in high resolution by Fourier spectrometry in the range 2500–15 000 cm −1. The precision of the measurements is estimated to be about 0.003 cm −1. We have analyzed 19 bands of the W 3Δ u - B 3Π g system of 14N 2, with 0 ≤ v′ ≤ 7, and three bands of 15N 2 lying between 2500 and 5900 cm −1. The molecular constants of the 3Δ u and B 3Π g states have been determined by direct approach using an iterative nonlinear least-squares procedure. It has proved convenient to describe the levels of W 3Δ u state in a case a basis although in fact they approximate those of Hund's case b. Derived values of equilibrium constants of W 3Δ u are, in cm −1: T e = 8875.3347 (with origin taken in A, 3Σ u + v = 0 level); ω e = 1506.4859; ω e χ e = 12.5469; B e = 1.4702537; α B = 0.0170389; D e = 0.55958 × 10 −5. RKR potential energy curves for the two states are constructed, and the Franck-Condon factors calculated for the W- B system.