On the possibility of detecting tetraazatetrahedrane (N4) in liquid or solid nitrogen by Fourier transform Raman spectroscopy

The detection limit of N-4 (at T-d and D-2h symmetry) by the Fourier transform (FT) Raman technique was determined in liquid and solid nitrogen using a modified commercial FT-Raman spectrometer. The detection limit was determined by combining experimental signal strength and noise levels of N-2 in liquid and solid nitrogen with nb initio quantum mechanical (QM) calculations of the Raman intensities of N-2 and N-4 (T-d and Du,). The QM calculations were performed at the B3LYP/6-311G(d) level. The detection limit was found to be 34 ppm of N-4(T-d) in N-2(liq) and 80 ppm in N-2(solid), using an 8 h measurement time and a laser power of 1000 mW. The paper also reports calculated Raman spectra of N-4 (T-d and D-2h) at the B3LYP/6-311G(d) level and a new harmonic wavenumber scaling factor, s = 0.953447, for nitrogen-containing molecules at the B3LYP/6-311G(d) level. The Raman spectrum of N-4(T-d) consists of three lines, at 728.35, 938.93 and 1321.58 cm(-1), with Raman scattering activities of 17.5, 36.2 and 30.0 Angstrom (4) u(-1) respectively. Copyright (C) 2001 John Wiley & Sons, Ltd.