Liang Hao, Zhou Zhengfang, Hua Zefeng, Zhao Yunxiao, Feng Shaowen, Chen Yang, Zhao Dongfeng
CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemical Physics , University of Science and Technology of China , Hefei , Anhui 230026 , P.R. China.
J Phys Chem A. 2019 May 30;123(21):4609-4615. doi: 10.1021/acs.jpca.9b03211. Epub 2019 May 17.
The AΠ-XΠ and 1Σ-XΠ electronic transition spectra of Br have been studied in the 500-720 nm wavelength range in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The cryogenic ion trap produces a rotationally and vibrationally cold mass selected ion beam of Br, which simplifies the experimental spectra from vibrational hot bands and bands of mixed isotopic species. Vibrationally resolved photofragment excitation spectra are recorded for individual isotopologues of Br (Br, BrBr, Br) by [1+1] two-photon dissociation spectroscopy. Velocity map imaging of the photofragmented Br ions provides complementary information in the determination of spin-orbit states involved in corresponding electronic transitions. An experimental identification of the 1Σ state has becomes possible based on the present experimental results and previously reported theoretical calculations. Vibrational analyses of the photofragment excitation spectra have yielded spectroscopic parameters, including state origins, harmonic frequencies, and anharmonic constants, for both AΠ and 1Σ states. The observed AΠ state spin-orbit splitting and the "spin-forbidden" 1Σ-XΠ transition band intensities indicate considerable spin-orbit couplings between the 1Σ and AΠ states. In addition, two groups of weak vibrational bands are also observed in the experimental spectra of BrBr, which may be due to symmetry-forbidden transitions from the XΠ ground state to low-lying gerade states.
利用低温圆柱形离子阱速度成像光谱仪，在冷离子束中对溴的AΠ-XΠ和1Σ-XΠ电子跃迁光谱进行了500 - 720 nm波长范围的研究。低温离子阱产生了一个转动和振动温度低的、质量选择的溴离子束，这简化了来自振动热谱带和混合同位素物种谱带的实验光谱。通过[1+1]双光子解离光谱法，对溴的各个同位素分子（Br、BrBr、Br）记录了振动分辨的光碎片激发光谱。光碎片溴离子的速度成像在确定相应电子跃迁所涉及的自旋轨道态方面提供了补充信息。基于目前的实验结果和先前报道的理论计算，对1Σ态进行实验识别成为可能。对光碎片激发光谱的振动分析得出了AΠ和1Σ态的光谱参数，包括态起源、谐波频率和非谐常数。观测到的AΠ态自旋轨道分裂和“自旋禁戒”的1Σ-XΠ跃迁带强度表明1Σ和AΠ态之间存在相当大的自旋轨道耦合。此外，在BrBr的实验光谱中还观测到两组弱振动谱带，这可能是由于从XΠ基态到低能级 gerade态的对称禁戒跃迁所致。
