Deselnicu Mihaela, Tao Chong, Mukarakate Calvin, Reid Scott A
Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, USA.
J Chem Phys. 2006 Apr 7;124(13):134302. doi: 10.1063/1.2183302.
We report fluorescence excitation and emission spectra of CHBr in the 450-750 nm region. A total of 30 cold bands involving the pure bending levels 2(0)(n) with n=2-8 and combination bands 2(0)(n)3(0)(1)(n=1-8), 2(0) (n)3(0)(2)(n=1-6), 2(0)(n)3(0)(3)(n=1-2), 1(0)(1)2(0)(n)(n=5-7), 1(0)(1)2(0)(n)3(0)(1)(n=4-6), and 1(0)(1)2(0)(n)3(0)(2)(n=5) in the A (1)A(")<--X (1)A(') system were observed, in addition to a number of hot bands. The majority of these are reported and/or rotationally analyzed here for the first time. Spectra were measured under jet-cooled conditions using a pulsed discharge source, and rotational analysis yielded band origins and rotational constants for both bromine isotopomers (CH (79)Br,CH (81)Br). The derived A (1)A(") vibrational intervals are combined with results of [Yu et al. J. Chem. Phys. 115, 5433 (2001)] to derive barriers to linearity for the 2(n), 2(n)3(1), and 2(n)3(2) progressions. The A (1)A(") state C-H stretching frequency is determined here for the first time, and the observed nu(3) dependence of the (79)Br-(81)Br isotope splitting in the A(1)A(") state is in good agreement with theoretical expectations. Our dispersed fluorescence spectra probe the vibrational structure of the X(1)A(') state up to approximately 9000 cm(-1) above the vibrationless level; the total number of levels observed is more than twice that previously reported. As first reported by [Chen et al. J. Mol. Spectrosc. 209, 254 (2001)], these spectra reveal numerous perturbations due to spin-orbit interaction with the low-lying a(3)A(") state. The results of a Dunham expansion fit of the ground state vibrational term energies, and comparisons with previous experimental and theoretical studies, are reported. Our results lead to several revised assignments, including the X (1)A(') C-H stretching fundamental. Globally, the vibrational frequencies of X(1)A('), a(3)A("), and A(1)A(") are in excellent agreement with theoretical predictions.
我们报告了CHBr在450 - 750 nm区域的荧光激发和发射光谱。总共观察到30个冷带，涉及纯弯曲能级2(0)(n)（n = 2 - 8）以及组合带2(0)(n)3(0)(1)（n = 1 - 8）、2(0)(n)3(0)(2)（n = 1 - 6）、2(0)(n)3(0)(3)（n = 1 - 2）、1(0)(1)2(0)(n)（n = 5 - 7）、1(0)(1)2(0)(n)3(0)(1)（n = 4 - 6）和1(0)(1)2(0)(n)3(0)(2)（n = 5），这些都在A (1)A(")<--X (1)A(')体系中，此外还观察到一些热带。其中大部分在此首次进行了报道和/或转动分析。光谱是在喷射冷却条件下使用脉冲放电源测量的，转动分析得出了两种溴同位素异构体（CH (79)Br、CH (81)Br）的带起源和转动常数。推导得到的A (1)A(")振动间隔与[Yu等人，《化学物理杂志》115, 5433 (2001)]的结果相结合，以推导2(n)、2(n)3(1)和2(n)3(2)跃迁的线性化势垒。这里首次确定了A (1)A(")态的C - H伸缩频率，并且观察到A(1)A(")态中(79)Br - (81)Br同位素分裂的ν(3)依赖性与理论预期高度吻合。我们的色散荧光光谱探测了X(1)A(')态高达比无振动能级高约9000 cm(-1)的振动结构；观察到的能级总数比之前报道的多两倍以上。正如[Chen等人，《分子光谱学杂志》209, 254 (2001)]首次报道的那样，这些光谱揭示了由于与低激发a(3)A(")态的自旋 - 轨道相互作用而产生的大量微扰。报告了基态振动项能量的邓纳姆展开拟合结果，以及与之前实验和理论研究的比较。我们的结果导致了一些修正的归属，包括X (1)A(') C - H伸缩基频。总体而言，X(1)A(')、a(3)A(")和A(1)A(")的振动频率与理论预测高度吻合。
