Anomalous Intensities in the 2+1 REMPI Spectrum of the E-X Transition of CO
Anomalous Intensities in the 2+1 REMPI Spectrum of the E-X Transition of CO
复制标题
CO E-X 跃迁 2 1 REMPI 谱中的异常强度
DOI：
10.1021/acs.jpca.9b00109
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
North, S. W.
中科院分区：
文献类型：
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作者：
Gunthard, C. E.;Wallace, C. J.;Hall, G. E.;Field, R. W.;North, S. W.
我们报道了在214 nm附近的单色实验，涉及到喷射冷却OCS的光解产生CO（X1 ~+，v = 0，1）的高转动态（40 <J< 80），然后通过E1 ~+态被2+1共振增强多光子电离。名义上禁止的Q分支的双光子E1Π-X1 π +跃迁的观察强度可比的允许的R分支。高JQ-分支线的明亮特征可以定量地描述为由于E 1 Π和C 1 π +态的混合而引起的强度借用，使用J依赖的混合系数，从在E态的低转动能级中观察到的Λ-加倍外推。除了Q分支强度的显著增强超过传统的双光子线强度预测的a1Π-1 π +跃迁的值之外，R分支和P分支的高J线的强度与未扰动的低J线强度相比似乎被抑制了大约3倍，这很可能是由于与a1 π-态相关的扰动。由本谱导出的J < 80，v = 0的E态转动项值与根据J < 50的转动能级导出的分子常数外推的结果在我们的测量和校准不确定度范围内是一致的。的E-X过渡是有吸引力的未来应用的光解动力学和旋转极化测量的CO光碎片，方便地访问多个旋转分支，表现出不同的灵敏度片段对齐的状态选择性探测。
We report on one-color experiments near 214 nm involving the photodissociation of jet-cooled OCS to produce high rotational states (40 <J< 80) of CO (X1Σ+, v = 0, 1) which were then ionized by 2+1 resonance-enhanced multiphoton ionization via the E1Π state. The nominally forbidden Q-branch of the two-photon E1Π–X1Σ+transition is observed with intensity comparable to the allowed R-branch. The bright character of the high-JQ-branch lines can be described quantitatively as intensity borrowing due to mixing of the E1Π and C1Σ+states, usingJ-dependent mixing coefficients extrapolated from the observed Λ-doubling in the lower rotational levels of the E state. In addition to the significant enhancement of Q-branch intensities above the values predicted by conventional two-photon line strengths for a1Π–1Σ+transition, the high-Jlines of the R- and P-branches appear to be suppressed in intensity by approximately a factor of 3 compared to the unperturbed low-Jline strengths, most likely due to perturbations associated with a1Σ–state. The E-state rotational term values forJ< 80, v = 0 derived from the present spectra agree within our measurement and calibration uncertainties with the extrapolations based on the molecular constants previously derived from rotational levels withJ< 50. The E–X transition is attractive for future application to photodissociation dynamics and rotational polarization measurements of CO photofragments, with convenient access to state-selective probing on multiple rotational branches, which exhibit different sensitivity to fragment alignment.