Marr AJ, North SW, Sears TJ, Ruslen L, Field RW
Department of Chemistry, Brookhaven National Laboratory, Upton, New York, 11973-5000
J Mol Spectrosc. 1998 Mar;188(1):68-77. doi: 10.1006/jmsp.1997.7500.
We report the observation and assignment of new high-resolution spectra of the A1A" <-- X1A' transition of bromomethylene, HCBr, obtained by transient laser absorption spectroscopy at near-infrared wavelengths. The 2(1)0 band of HCBr (nu0 = 11 957 cm-1) and the 2(2)0 band of DCBr (nu0 = 12 349 cm-1) have been observed for both naturally occurring isotopes of bromine. The c-type rotational branches of the Ka = 0 <-- 1 subbands have been assigned in detail. Other subbands have been partially assigned, but their detailed rotational quantum number analysis has not yet proved possible. Their presence does, however, indicate that the molecule exhibits nonlinear rotational structure in these vibrational levels, in contrast to what was found for the A1A" (0, 2, 0) level of HCBr (nu0 = 12 786 cm-1) [B. C. Chang and T. J. Sears, J. Chem. Phys. 105, 2135-2140 (1996)]. Analysis of the rotational structure in the spectra reported here has required a reassessment of certain rotational assignments of that previous work. We now find that the lower singlet state is isolated; there is no evidence of triplet state perturbations. Rotational constants derived for the ground state of all the naturally occurring isotopomers were used to estimate structural parameters. A barrier to linearity for the A1A" state, 13 590 cm-1 above the zero point level of the ground X1A' state, is estimated. Copyright 1998 Academic Press.
我们报告了通过近红外波长的瞬态激光吸收光谱法获得的溴代亚甲基（HCBr）的A1A" ← X1A'跃迁的新高分辨率光谱的观测和归属。对于溴的两种天然同位素，均观测到了HCBr的2(1)0带（ν0 = 11957 cm-1）和DCBr的2(2)0带（ν0 = 12349 cm-1）。详细归属了Ka = 0 ← 1子带的c型转动分支。其他子带已部分归属，但尚未证明能够对其进行详细的转动量子数分析。然而，它们的存在确实表明，与HCBr（ν0 = 12786 cm-1）的A1A" (0, 2, 0)能级的情况[B. C. 张和T. J. 西尔斯，《化学物理杂志》105, 2135 - 2140 (1996)]相反，该分子在这些振动能级中表现出非线性转动结构。对本文报道的光谱中的转动结构进行分析需要重新评估之前工作中的某些转动归属。我们现在发现较低的单重态是孤立的；没有三重态微扰的证据。利用为所有天然同位素异构体的基态导出的转动常数来估计结构参数。估计了A1A"态相对于基态X1A'零点能级上方13590 cm-1处的线性势垒。版权所有1998年，学术出版社。
