Fourier Transform Emission Spectroscopy of the Low-Lying Electronic States of NbN

The high-resolution spectrum of NbN has been investigated in emission in the 3000-15 000 cm(-1) region using a Fourier transform spectrometer. The bands were excited in a microwave discharge through a mixture of NbCl(5) vapor, approximately 5 mTorr of N(2), and 3 Torr of He. Numerous bands observed in the near-infrared region have been classified into the following transitions: f(1)Phi-c(1)Gamma, e(1)Pi-a(1)Delta, C(3)Pi(0+)-A(3)Sigma(-)(1), C(3)Pi(0-)-A(3)Sigma(-)(1), C(3)Pi(1)-a(1)Delta, C(3)Pi(1)-A(3)Sigma(-)(0), d(1)Sigma(+)-A(3)Sigma(-)(0), and d(1)Sigma(+)-b(1)Sigma(+). These observations are consistent with the energy level diagram provided by laser excitation and emission spectroscopy [Y. Azuma, G. Huang, M. P. J. Lyne, A. J. Merer, and V. I. Srdanov, J. Chem. Phys. 100, 4138-4155 (1993)]. The missing d(1)Sigma(+) state has been observed for the first time and its spectroscopic parameters are consistent with the theoretical predictions of S. R. Langhoff and W. Bauschlicher, Jr. [J. Mol. Spectrosc. 143, 169-179 (1990)]. Rotational analysis of a number of bands has been obtained and improved spectroscopic parameters have been extracted for the low-lying electronic states. The observation of several vibrational bands with v = 1 has enabled us to determine the vibrational intervals and equilibrium bond lengths for the A(3)Sigma(-)(0), a(1)Delta, b(1)Sigma(+), d(1)Sigma(+), and C(3)Pi(1) states. Copyright 2000 Academic Press.