IR Spectra and Vibrational Analysis of Isotopomers of KNO3in Solid Ar

• DOI: 10.1006/jmsp.1997.7265
• Publication Date: 2003-04-23T18:35:11Z
• Authors: Wen-Jui Lo; Min-yi Shen; Chin-hui Yu; Yuan-Pern Lee
• Keywords: Isotopomers; Fermi resonance; Matrix Isolation

Abstract Infrared absorption spectra of M NO 3 ( M = Li, Na, and K) in solid Ar were recorded with a FTIR spectrometer. The absorption of KNO 3 displayed only singlet lines, at 1460.3, 1293.5, 1031.4, 828.0, 721.4, and 709.4 cm −1 , whereas that of LiNO 3 and of NaNO 3 showed doublets or multiplets due to matrix site splitting. Hence, detailed vibrational analysis of the NO 3 − moiety was made for KNO 3 . From spectra of KN 16 O 3− x 18 O x ( x = 0–3) and K 15 NO 3 , five vibrational modes are unambiguously assigned and a bidentate structure of KNO 3 is confirmed. The line at 721.4 cm −1 , previously assigned to a B 2 mode, is reassigned to the ν 3 ( A 1 ) mode. A weak line at 709.4 cm −1 , of which 18 O-isotopic data are lacking, is tentatively assigned to the ν 8 ( B 2 ) mode. A Fermi resonance due to the ν 1 ( A 1 ) and a combinational band of ν 7 ( B 2 ) + ν 9 ( B 2 ) was observed for K( 18 O 18 O)N 16 O at 1465.8 and 1451.7 cm −1 . Normal coordinate analysis was performed for the five vibrational modes of all isotopic species. The results are consistent with theoretical predictions using density functional theory (B3-LYP).