School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom.
J Chem Phys. 2011 Dec 21;135(23):234304. doi: 10.1063/1.3665135.
A combined theoretical and experimental study of the depolarization of selected NO(X(2)Π, v = 0, j, F, ɛ) levels in collisions with a thermal bath of Ar has been carried out. Rate constants for elastic depolarization of rank K = 1 (orientation) and K = 2 (alignment) were extracted from collision-energy-dependent quantum scattering calculations, along with those for inelastic population transfer to discrete product levels. The rate constants for total loss of polarization of selected initial levels, which are the sum of elastic depolarization and population transfer contributions, were measured using a two-color polarization spectroscopy technique. Theory and experiment agree qualitatively that the rate constants for total loss of polarization decline modestly with j, but the absolute values differ by significantly more than the statistical uncertainties in the measurements. The reasons for this discrepancy are as yet unclear. The lack of a significant K dependence in the experimental data is, however, consistent with the theoretical prediction that elastic depolarization makes only a modest contribution to the total loss of polarization. This supports a previous conclusion that elastic depolarization for NO(X(2)Π) + Ar is significantly less efficient than for the electronically closely related system OH(X(2)Π) + Ar [P. J. Dagdigian and M. H. Alexander, J. Chem. Phys. 130, 204304 (2009)].
我们对选定的 NO(X(2)Π，v = 0，j，F，ɛ)能级在与 Ar 热浴碰撞过程中的去极化进行了理论和实验的综合研究。从与碰撞能量有关的量子散射计算中，我们提取了 K = 1（取向）和 K = 2（排列）的弹性去极化的速率常数，以及向离散产物能级的非弹性布居转移的速率常数。使用双色偏振光谱技术测量了选定初始能级的总极化损失的速率常数，它是弹性去极化和布居转移贡献的总和。理论和实验定性地一致，即总极化损失的速率常数随 j 的增加而略有下降，但绝对值的差异远远超过测量的统计不确定度。目前尚不清楚造成这种差异的原因。实验数据中缺乏明显的 K 依赖性与理论预测一致，即弹性去极化对总极化损失的贡献很小。这支持了先前的结论，即与电子上密切相关的 OH(X(2)Π) + Ar 系统相比，NO(X(2)Π) + Ar 中的弹性去极化效率显著降低。
