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BH2 revisited: New, extensive measurements of laser-induced fluorescence transitions and ab initio calculations of near-spectroscopic accuracy
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2015-05-01 13:00:26 , DOI: 10.1063/1.4919094
Fumie X. Sunahori 1 , Mohammed Gharaibeh 2 , Dennis J. Clouthier 3 , Riccardo Tarroni 4
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2015-05-01 13:00:26 , DOI: 10.1063/1.4919094
Fumie X. Sunahori 1 , Mohammed Gharaibeh 2 , Dennis J. Clouthier 3 , Riccardo Tarroni 4
Affiliation
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The spectroscopy of gas phase BH2 has not been explored experimentally since the pioneering study of Herzberg and Johns in 1967. In the present work, laser-induced fluorescence (LIF) spectra of the A ̃ 2 B 1 ( Π u ) − X ̃ 2A1 band system of 11BH2, 10BH2, 11BD2, and 10BD2 have been observed for the first time. The free radicals were “synthesized” by an electric discharge through a precursor mixture of 0.5% diborane (B2H6 or B2D6) in high pressure argon at the exit of a pulsed valve. A total of 67 LIF bands have been measured and rotationally analyzed, 62 of them previously unobserved. These include transitions to a wide variety of excited state bending levels, to several stretch-bend combination levels, and to three ground state levels which gain intensity through Renner-Teller coupling to nearby excited state levels. As an aid to vibronic assignment of the spectra, very high level hybrid ab initio potential energy surfaces were built starting from the coupled cluster singles and doubles with perturbative triples (CCSD(T))/aug-cc-pV5Z level of theory for this seven-electron system. In an effort to obtain the highest possible accuracy, the potentials were corrected for core correlation, extrapolation to the complete basis set limit, electron correlation beyond CCSD(T), and diagonal Born-Oppenheimer effects. The spin-rovibronic states of the various isotopologues of BH2 were calculated for energies up to 22 000 cm−1 above the X ̃ (000) level without any empirical adjustment of the potentials or fitting to experimental data. The agreement with the new LIF data is excellent, approaching near-spectroscopic accuracy (a few cm−1) and has allowed us to understand the complicated spin-rovibronic energy level structure even in the region of strong Renner-Teller resonances.
中文翻译：
再次探讨BH2：激光诱导的荧光跃迁的新的广泛测量和近光谱精度的从头算
气相BH 2的光谱自1967年对Herzberg和Johns进行开创性研究以来，还没有进行过实验性探索。在目前的工作中，A ̃ 2 B 1（u u）− X ̃）-X ̃）-X ̃ 2阿1个的带系统11 BH 2，10 BH 2，11 BD 2，和10 BD 2已被观察到的第一次。通过放电通过0.5％乙硼烷（B 2 H 6或B 2 D 6）在脉冲阀出口处的高压氩气中）。总共对67个LIF频段进行了测量和旋转分析，其中62个以前未被观察到。这些包括过渡到各种各样的激发态弯曲能级，几个拉伸弯曲组合能级和三个基态能级，它们通过Renner-Teller耦合到附近的激发态能级获得强度。为了对光谱进行振动分配，非常高水平的混合 从头算 从这个七电子系统的理论三级扰动三元组（CCSD（T））/ aug-cc-pV5Z的耦合簇单，双开始，构建了势能面。为了获得最大可能的精度，对电势进行了校正，包括磁芯相关性，外推到完整的基集极限，超出CCSD（T）的电子相关性以及对角的Born-Oppenheimer效应。计算了BH 2的各种同位素的自旋流电子态，能量高达22000 cm -1高于X ̃（000）的水平，而无需对电位进行任何经验调整或不适合实验数据。与新的LIF数据的一致性非常好，接近近光谱精度（几cm -1），即使在强烈的Renner-Teller共振区域，也使我们能够了解复杂的自旋-核电子能级结构。
更新日期：2015-05-02
中文翻译：
再次探讨BH2：激光诱导的荧光跃迁的新的广泛测量和近光谱精度的从头算
气相BH 2的光谱自1967年对Herzberg和Johns进行开创性研究以来，还没有进行过实验性探索。在目前的工作中，A ̃ 2 B 1（u u）− X ̃）-X ̃）-X ̃ 2阿1个的带系统11 BH 2，10 BH 2，11 BD 2，和10 BD 2已被观察到的第一次。通过放电通过0.5％乙硼烷（B 2 H 6或B 2 D 6）在脉冲阀出口处的高压氩气中）。总共对67个LIF频段进行了测量和旋转分析，其中62个以前未被观察到。这些包括过渡到各种各样的激发态弯曲能级，几个拉伸弯曲组合能级和三个基态能级，它们通过Renner-Teller耦合到附近的激发态能级获得强度。为了对光谱进行振动分配，非常高水平的混合 从头算 从这个七电子系统的理论三级扰动三元组（CCSD（T））/ aug-cc-pV5Z的耦合簇单，双开始，构建了势能面。为了获得最大可能的精度，对电势进行了校正，包括磁芯相关性，外推到完整的基集极限，超出CCSD（T）的电子相关性以及对角的Born-Oppenheimer效应。计算了BH 2的各种同位素的自旋流电子态，能量高达22000 cm -1高于X ̃（000）的水平，而无需对电位进行任何经验调整或不适合实验数据。与新的LIF数据的一致性非常好，接近近光谱精度（几cm -1），即使在强烈的Renner-Teller共振区域，也使我们能够了解复杂的自旋-核电子能级结构。
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