HIGH-RESOLUTION INFRARED-SPECTRUM AND ANALYSIS OF THE V11,A2U(B2) FUNDAMENTAL-BAND OF 12C6H6 AND 13C12C5H6

High-resolution interferometric Fourier-transform infrared (instrumental bandwidth 0-0024cm-1) and diode-laser (0-001 cm-1) spectra have been taken for the natural isotopic mixture of benzene in the range 640-710cm-1. Accurate rotational-vibrational constants have been obtained for the fundamental v11 (67397465cm-1) of12C6H6 and for13C12C5H6 (v0 = 6736092 cm-1). Three hot bands have been analysed for 12C6H6 (v11 + v6 -v6, 673-50873 cm-1; vu + v16 - v16, 672-87601 cm-1; and 2v11-v11, 6741021cm-1). The results are discussed in relation to anharmonic and rotational-vibrational interaction constants and to force-field calculations. An analysis of available data for the ground-state rotational constant B0 is presented, which shows rather large systematic discrepancies. All high-resolution results are consistent with B0 = 5689-16 + 0-3 MHz, where the absolute error estimate is 50 times the standard deviation from the present, most precise determination. © 1990 Taylor & Francis Group, LLC.