Tong Xin, Cerný Jirí, Müller-Dethlefs Klaus, Dessent Caroline E H
The Photon Science Institute, Alan Turing Building, the School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK.
J Phys Chem A. 2008 Jul 3;112(26):5866-71. doi: 10.1021/jp710997q. Epub 2008 Jun 6.
Two conformational isomers of the aromatic hydrocarbon n-butylbenzene have been studied using two-color MATI (mass analyzed threshold ionization) spectroscopy to explore the effect of conformation on ionization dynamics. Cationic states of g auche-conformer III and anti- conformers IV were selectively produced by two-color excitation via the respective S 1 origins. Adiabatic ionization potentials of the gauche- and anti-conformations were determined to be 70146 and 69872 +/- 5 cm (-1) respectively. Spectral features and vibrational modes are interpreted with the aid of MP2/cc-pVDZ ab initio calculations, and ionization-induced changes in the molecular conformations are discussed. Complete basis set (CBS) ab initio studies at MP2 level reveal reliable energetics for all four n-butylbenzene conformers observed in earlier two-color REMPI (resonance enhanced multiphoton ionization) spectra. For the S 0 state, the energies of conformer III, IV and V are above conformer I by 130, 289, 73 cm (-1), respectively. Furthermore, the combination of the CBS calculations with the measured REMPI, MATI spectra allowed the determination of the energetics of all four conformers in the S 1 and D 0 states.
利用双色质量分析阈值电离（MATI）光谱研究了芳烃正丁基苯的两种构象异构体，以探讨构象对电离动力学的影响。通过分别经由各自的S1原点进行双色激发，选择性地产生了顺式构象异构体III和反式构象异构体IV的阳离子态。确定顺式和反式构象的绝热电离势分别为70146和69872±5 cm-1。借助MP2/cc-pVDZ从头算计算对光谱特征和振动模式进行了解释，并讨论了电离引起的分子构象变化。在MP2水平上的完全基组（CBS）从头算研究揭示了在早期双色共振增强多光子电离（REMPI）光谱中观察到的所有四种正丁基苯构象异构体的可靠能量学。对于S0态，构象异构体III、IV和V的能量分别比构象异构体I高130、289、73 cm-1。此外，CBS计算与测得的REMPI、MATI光谱相结合，使得能够确定S1和D0态中所有四种构象异构体的能量学。
