15min:

ROBERT L. SAMS, THOMAS A. BLAKE AND STEVEN W. SHARPE, Pacific Northwest National Laboratory, P. O. Box 999, Mail Stop K8-88, 3020 Q Avenue, Richland, WA 99352.

We have re-examined the ₄ bands (Herzberg numbering) of C₆H₆ and C₆D₆ using high resolution (0.0015 cm^-1) Fourier transform infrared spectroscopy. The spectra were taken with the benzene samples in a temperature stabilized cell (4 ^\circC), 20 cm in length. The -h6 sample spectrum (99.95 atom % ¹²C₆) was recorded with an MCT detector and KBr beamsplitter and the -d6 sample spectrum was recorded with a silicon bolometer detector and mylar beamsplitter. For the ₄ band of C₆H₆, we have fit the following preliminary spectroscopic constants: ₀ = 673.9747(2) cm^-1, B' = 0.1896388(13) cm^-1, (C' - B') - (C'' - B'') = 1.709(2)× 10^-4 cm^-1, D_J' = 4.106(60)× 10^-8 cm^-1, D_K' - D_K'' = -2.9(9)× 10^-10 cm^-1, D_JK' = -6.89(6)× 10^-8 cm^-1, B'' = 0.1897739(10) cm^-1, D_J'' = 4.123(45)× 10^-8 cm^-1, D_JK'' = -6.94(5)× 10^-8 cm^-1. For the ₄ band of C₆D₆, we have fit the following preliminary spectroscopic constants: ₀ = 496.2086(1) cm^-1, B' = 0.156919(5) cm^-1, and B'' = 0.157016(5) cm^-1. Band centers of the observed sequences of hot bands for both isotopic modifications will be reported.