Rotationally resolved electronic excitation spectra of the ethoxy ~B .rarw. ~X transition
Rotationally resolved electronic excitation spectra of the ethoxy ~B .rarw. ~X transition
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乙氧基〜B的旋转分辨电子激发光谱.rarw。
DOI：
10.1021/j100139a010
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
T. Miller
中科院分区：
文献类型：
--
作者：
X. Tan;J. Williamson;S. C. Foster;T. Miller
记录了乙氧基自由基近紫外电子跃迁的0：和9：带的高分辨电子激发光谱。乙氧基自由基产生的自由射流膨胀由亚硝酸乙酯（CzHsONO）的光解。两个光谱都具有约400 MHz的线宽。一个完整的旋转光谱分析表明，乙氧基的电子跃迁是C-型（垂直）和基态的自旋-旋转分裂是完全解决，而激发态的自旋-旋转分裂没有解决。的自旋-旋转参数进行比较，相应的自旋-旋转参数的密切相关的自由基，甲氧基和乙烯氧基。我呢？本文报道了近紫外区B ZA' - X 2 A”电子跃迁的喷流冷却激光诱导荧光光谱，其分辨率足以观察到转动线的各个自旋转动分量。我们的分析提供了精确的值，所有三个转动常数在地面和激发B状态，以及在地面状态的自旋转动张量的主要成分。的旋转常数进行了比较从头计算结构predictionZ 0的地面siate和用于推断的几何变化的激发态B没有从头计算存在。(Not?我们将把这种跃迁中的激发态称为B态，尽管它有时被称为A态。正如我们的分析所示，应该有一个尚未观察到的乙氧基的低位A A'态。）并与方法中类似量的实测值进行了比较。14在数值上，乙氧基的数值比乙烯氧基的数值更接近甲氧基。乍一看，这是相当令人惊讶的，因为在甲氧基的基态，特别是em，被认为是唯一大的，因为与简并电子态的Jahn-Teller失真相关的效应。由于甲基取代甲氧基中的氢形成乙氧基消除了电子简并性，乙氧基中的coo值可能更接近乙烯氧基的非简并基态。然而，匡威的实验结果可以合理化，给出某些合理的假设，乙氧基和乙烯氧基的电子结构。
High-resolution electronic excitation spectra of the 0: and the 9; bands of the near-UV electronic transition of the ethoxy radical have been recorded. The ethoxy radical was produced in a free-jet expansion by photodissociation of ethyl nitrite (CzHsONO). Both spectra have a linewidth of about 400 MHz. A complete rotational analysis of the spectrum indicates that the electronic transition of ethoxy is C-type (perpendicular) and the ground-state spin-rotation splittings are fully resolved, while the excited state spin-rotation splittings are not resolved. The spin-rotational parameters are compared to the corresponding spin-rotational parameters of the closely related radicals, methoxy and vinoxy. I? this paper, we report the jet-cooled LIF spectra of the B ZA' - X 2A" electronic transition in the near-UV, with sufficient resolution to observe individual spin-rotation components of rotational lines. Our analysis provides accurate values-for all three rotational constants in both the ground and excited B state, as well as the principal components of the spin rotation tensor in the ground state. The rotational constants are compared with ab initio structural predictionsZ0 for the ground siate and are used to infer the geometric changes in the excited B state for which no ab initio calculations exist. (Not? that we shall refer to the excited state in this transition as the B state, even though it has been sometimes referred to as the A state. As our analysis shows, there should be an as yet unobserved low-lying A A' state of ethoxy .) compared with the pkviously measured values of the analogous quantities in metho~y'.~~ and vinoxy radicals.14 Numerically, the values in ethoxy are much closer to those of methoxy than vinoxy. At first glance, this is quite surprising because in the ground state of methoxy, particularly em, is thought21 to be uniquely large because of an effect associated with the Jahn- Teller distortion of a degenerate electronic state. Since the substitution of a methyl group for hydrogen in methoxy to form ethoxy removes the electronic degeneracy, the value of coo in ethoxy might be expected to be much closer to that of the nondegenerate ground state of vinoxy. However, the converse experimental finding can be rationalized, given certain reasonable assumptions about the electronic structure of ethoxy and vinoxy.