High-resolution Fourier-transform emission spectroscopy of the A ^4Π-X ^4Σ^- system of WN

Abstract

The electronic emission spectrum of WN has been observed in the 500–580-nm spectral region with a Fourier-transform spectrometer. The bands were excited in a tungsten hollow-cathode lamp in the presence of a trace of molecular nitrogen. The observed bands have been assigned to the A4Π–X4∑− transition. The ground state is a regular 4∑− state belonging to Hund’s coupling case (a′). The principal ground-state constants obtained from the fit of the observed lines are B0=0.4663779(62),D0=3.5847(77)×10−7,γ0=0.051862(21)cm−1.The excited state, on the other hand, shows Hund’s case (c) tendencies with the spin components mixed because of interactions with other neighboring states. There have been no previous observations of the WN molecule to our knowledge.