Lucchese Robert R, Bozek John D, Das Aloke, Poliakoff E D
Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA.
J Chem Phys. 2009 Jul 28;131(4):044311. doi: 10.1063/1.3180817.
The vibrational branching ratios in the photoionization of C(6)F(6) leading to the C (2)B(2u) state of C(6)F(6)(+) are considered. Computational and experimental data are compared for the excitation of two totally symmetric modes. Resonant features at photon energies near 19 and 21 eV are found. A detailed analysis of the computed results shows that the two resonance states have different responses to changes in the C-C and C-F bond lengths. We find that the energies of both of the resonant states decrease with increasing bond lengths. In contrast to the energy positions, however, the resonant widths and the integrated oscillator strength of the resonances can either increase or decrease with increasing bond length depending on the nature and location of the resonant state and the location of the bond under consideration. With increasing C-F bond length, we find that the energy of the antibonding sigma resonance localized on the ring has a decreasing resonance energy and also a decreasing lifetime. This behavior is in contrast to the usual behavior of shape resonance energies where increasing a bond length leads to decreasing resonance energies and increasing resonance lifetimes. Finally, for the first time, we examine the effect of simultaneously occurring multiple vibrations on the resonance profile for valence photoionization, and we find that the inclusion of more than a single vibrational mode substantially attenuates the strength of resonance.
研究了六氟苯光致电离生成六氟苯离子（C(6)F(6)(+)）的C (2)B(2u)态时的振动分支比。比较了两种全对称模式激发的计算数据和实验数据。发现在光子能量接近19 eV和21 eV处存在共振特征。对计算结果的详细分析表明，两个共振态对碳 - 碳键和碳 - 氟键长度变化的响应不同。我们发现，两个共振态的能量均随键长增加而降低。然而，与能量位置不同，共振宽度和共振的积分振子强度可能会随着键长增加而增加或减少，这取决于共振态的性质和位置以及所考虑键的位置。随着碳 - 氟键长增加，我们发现定域在环上的反键σ共振的能量降低，寿命也缩短。这种行为与形状共振能量的通常行为相反，通常增加键长会导致共振能量降低和共振寿命增加。最后，我们首次研究了同时发生的多个振动对价层光致电离共振轮廓的影响，发现包含多个以上振动模式会大幅减弱共振强度。
