Institut fur Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
J Chem Phys. 2010 Jul 28;133(4):044311. doi: 10.1063/1.3464487.
We quantitatively determine cross sections for rotational decoherence from the decay of nonadiabatic laser-induced alignment in nitrogen and nitrogen-foreign gas mixtures in a temperature range between 80 K and room temperature. The cross section for rotational decoherence in pure nitrogen decreases from 102 A(2) at 80 K to 48 A(2) at 295 K, leading to long-lived coherences even at high temperatures. Comparison with the broadening of the transition lines of the Raman Q-branch reported in the literature shows that the decay of rotational coherence proceeds at the same rate as rotational depopulation. This is verified also for mixtures of nitrogen with hydrogen, helium, argon, and krypton. We discuss limits posed by a possible J-dependence of the cross sections and strategies for state resolved determination from the time-dependent alignment signal.
我们定量地确定了从氮和氮-杂质气体混合物中非绝热激光诱导取向衰减中旋转退相干的截面，温度范围在 80 K 到室温之间。在纯氮中，旋转退相干的截面从 80 K 时的 102 A(2)下降到 295 K 时的 48 A(2)，即使在高温下也能保持长寿命的相干性。与文献中报道的喇曼 Q 分支跃迁线展宽的比较表明，旋转相干的衰减与旋转去激发的速率相同。对于氮与氢、氦、氩和氪的混合物也是如此。我们讨论了截面可能的 J 依赖性所带来的限制，并讨论了从时间相关的取向信号中进行状态分辨确定的策略。
