Valero Rosendo, Kroes Geert-Jan, Ekinci Yasin, Toennies J Peter
Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
J Chem Phys. 2006 Jun 21;124(23):234707. doi: 10.1063/1.2208361.
High probabilities of energy transfer from translation to molecular rotations are observed in the scattering of n-D(2) from LiF(001) at an incident beam energy of 85.3 meV. For the 100 incidence direction, close-coupling calculations yield ratios of the rotationally inelastic (j=0-->2) and (j=1-->3) peaks to the rotationally elastic specular peaks (G=0) that are in reasonable agreement with experiment, as are the ratios of the rotationally elastic diffraction peak intensities to the specular peak intensities. The agreement between theory and experiment is also quite good for the rotationally inelastic diffractive (-1-1) transitions for (j=1-->3), but rather poor for (j=0-->2). The calculations show that the interaction between the electrostatic field of the surface ions and the quadrupole moment of the D(2) molecule efficiently promotes the (j=0-->2) and (j=1-->3) transitions. If this electrostatic interaction is excluded from the potential model, the ratios of the (j=0-->2) and (j=1-->3) rotationally inelastic peaks to the corresponding specular peaks show a large discrepancy with experiment, underlining the importance of this interaction. The close-coupling calculations show a somewhat worse agreement with experiment for the 110 incidence direction. In particular, the sharp peaks observed experimentally in the ratios of the peak intensities of the rotationally inelastic G=0 (j=0-->2) and (j=1-->3) to the rotationally elastic G=0 transitions as a function of incident angle are not reproduced by the calculations. The theoretical ratios of the peak intensities of the rotationally elastic diffraction to G=0 transitions are shifted to lower incidence angles with respect to experiment. The rotationally inelastic diffractive (-10) transitions present an interesting resonance phenomenon for the (j=0-->2) rotational transition. This resonance is predicted by both theory and experiment, although at rather different incident angles.
在85.3毫电子伏特的入射束能量下，观察到n-D(2)从LiF(001)散射时能量从平移高效转移到分子转动。对于100入射方向，密耦计算得出转动非弹性（j = 0→2）和（j = 1→3）峰与转动弹性镜面反射峰（G = 0）的比率，与实验结果合理相符，转动弹性衍射峰强度与镜面反射峰强度的比率也是如此。对于（j = 1→3）的转动非弹性衍射（-1 -1）跃迁，理论与实验的一致性也相当好，但对于（j = 0→2）则相当差。计算表明，表面离子的静电场与D(2)分子的四极矩之间的相互作用有效地促进了（j = 0→2）和（j = 1→3）跃迁。如果从势模型中排除这种静电相互作用，（j = 0→2）和（j = 1→3）转动非弹性峰与相应镜面反射峰的比率与实验结果存在很大差异，突出了这种相互作用的重要性。密耦计算表明，对于110入射方向，与实验的一致性稍差。特别是，实验中观察到的转动非弹性G = 0（j = 0→2）和（j = 1→3）峰强度与转动弹性G = 0跃迁峰强度之比随入射角变化的尖锐峰未被计算重现。转动弹性衍射峰强度与G = 0跃迁的理论比率相对于实验向较低入射角偏移。对于（j = 0→2）转动跃迁，转动非弹性衍射（-10）跃迁呈现出有趣的共振现象。理论和实验都预测到了这种共振，尽管入射角相差较大。
