A NEW ROVIBRATIONAL ANALYSIS OF THE NU(2), NU(5) AND 2NU(3) BANDS OF MONOISOTOPIC (H3SIBR)-BR-79

A high-resolution FT infrared spectrum of (H3SiBr)-Br-79 (resolution 0 .0022 cm(-1)) in the region 830-1050 cm(-1) was used to analyze the fu ndamental bands nu(2) (A(1)) and upsilon(s) (E). A total of 4392 trans ition wavenumbers for nu(2) and nu(5) have been fitted, together with 632 energy values for the nu(3) = 2 level, with a standard deviation o f the fit of 0.123 x 10(-3) cm(-1). A model was used taking into accou nt the strong Coriolis x, y resonance between nu(2) and nu(5). and als o three local resonances: (i) an accidental Coriolis-type resonance of nu(5) with 2 nu 3 (crossing of (kl = -13, nu(5) = 1) and (K = 14, nu( 3) = 2) for J' between 16 and 17); (ii) an l(+/- 2, +/- 1) resonance o f the (kl = 2, nu(5) = 1) and (kl = -3, nu(5) = 1) levels, with a cros sing for J' between 58 and 59; and (iii) an accidental l(+/- 1, +/- 2) resonance between nu(2) (K = 3) and nu(5) (kl = 1, A(+) and A(-)). So me ''forbidden'' transitions, due to this last resonance, were observe d and included in the fit. The I-doubling constant q(5) and the Coriol is resonance parameters being strongly correlated, these two resonance s cannot be treated independently. Hence, q(5) was fixed at zero and a value of 0.09314238(58) cm(-1) was obtained for B zeta(25). (C) 1995 Academic Press, Inc.