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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Accurate determination of the structure of cyclohexane by femtosecond rotational coherence spectroscopy and Ab initio calculations
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Accurate determination of the structure of cyclohexane by femtosecond rotational coherence spectroscopy and Ab initio calculations

机译：飞秒旋转相干光谱和从头算计算准确测定环己烷的结构

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摘要

We combine femtosecond time-resolved rotational coherence spectroscopy with high-level ab initio theory to obtain accurate structural information for the nonpolar molecules cyclohexane (C_6H_(12)) and cyclohexane-d_(12) (C_6D_(12)). We measured the rotational B_0 and centrifugal distortion constants DJ, DJK of the v = 0 states of C_6H_(12) and C _6D_(12) to high accuracy, for example, B_0(C _6H_(12)) = 4306.08(5) MHz, as well as Bv for the vibrationally excited states ν_(32), ν_6, ν_(16) and ν_(24) of C_6H_(12) and additionally ν_(15) for C_6D_(12). To successfully reproduce the experimental RCS transient, the overtone and combination levels 2ν_(32), 3ν_(32), ν_(32) + ν_6, and ν_(32) + ν_(16) had to be included in the RCS model calculations. The experimental rotational constants are compared to those obtained at the second-order M?ller-Plesset (MP2) level. Combining the experimental and calculated rotational constants with the calculated equilibrium bond lengths and angles allows determination of accurate semiexperimental equilibrium structure parameters, for example, r_e(C-C) = 1.526 ± 0.001 ?, r_e(C-H_(axial)) = 1.098 ± 0.001 ?, and r_e(C-H_(equatorial)) = 1.093 ± 0.001 ?. The equilibrium C-C bond length of C_6H_(12) is only 0.004 ? longer than that of ethane. The effect of ring strain due to the unfavorable gauche interactions is mainly manifested as small deviations from the C-C-C, C-C-H_(axial), and C-C-H_(equatorial) angles from the tetrahedral value.
机译：我们将飞秒时间分辨旋转相干光谱与高级从头算术理论相结合，以获得非极性分子环己烷（C_6H_（12））和环己烷-d_（12）（C_6D_（12））的准确结构信息。我们以很高的精度测量了C_6H_（12）和C _6D_（12）的v = 0状态的旋转B_0和离心畸变常数DJ，DJK，例如B_0（C _6H_（12））= 4306.08（5）MHz ，以及C_6H_（12）的振动激发状态ν_（32），ν_6，ν_（16）和ν_（24）的Bv，以及C_6D_（12）的ν_（15）。为了成功地再现实验性RCS瞬态，RCS模型计算中必须包括泛音和组合电平2ν_（32），3ν_（32），ν_（32）+ν_6和ν_（32）+ν_（16）。将实验旋转常数与在二阶Müller-Plesset（MP2）水平获得的旋转常数进行比较。将实验和计算的旋转常数与计算的平衡键长度和角度相结合，可以确定准确的半实验平衡结构参数，例如，r_e（CC）= 1.526±0.001？，r_e（C-H_（轴向））= 1.098±0.001 ，并且r_e（C-H_（赤道））＝ 1.093±0.001Ω。 C_6H_（12）的平衡CC键长度只有0.004≤C≤C。比乙烷更长。由于不利的gauche相互作用而引起的环应变的影响主要表现为与四面体值的C-C-C，C-C-H_（轴向）角和C-C-H_（赤道）角略有偏差。

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