Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations
Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations
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通过瞬态红外光谱和主方程模拟研究光学离心 CO 分子的旋转能量传递动力学
DOI：
10.1039/d2fd00068g
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发表时间：
2022
影响因子：
3.4
通讯作者：
Mullin, Amy S
中科院分区：
文献类型：
--
作者：
Laskowski, Matthew R.;Michael, Tara J;Ogden, Hannah Marie;Alexander, M H;Mullin, Amy S
用实验和理论相结合的方法研究了光学离心法CO分子的量子态分辨转动能量转移动力学。在实验中，使用两个不同的光学离心机陷阱，一个具有光学离心机脉冲的全光谱带宽，另一个具有减小的带宽，在高达J=80的旋转态下获得了CO的反向旋转分布。基于高分辨率的瞬时红外吸收测量，确定了每个光阱倒置分布的高J尾部的弛豫动力学。在平行研究中，基于J=0-29的CO的双共振实验数据和符合统计幂指数能隙模型的数据，使用J=90状态下的CO-CO碰撞的状态-状态速率常数进行了主方程模拟。该模型与观测到的弛豫分布定性地符合，但观测到的衰变速率常数比模拟值小10倍。观测到的衰变速率常数也具有比模型预测的更强的J依赖关系。从角动量守恒和能量守恒的角度对结果进行了讨论，并与观察到的光学离心CO分子的取向各向异性衰减动力学进行了比较。通过考虑角动量效应，可以改进转动能量转移的模型。
A combined experimental and theoretical study of quantum state-resolved rotational energy transfer kinetics of optically centrifuged CO molecules is presented. In the experiments, inverted rotational distributions of CO in rotational states up to J = 80 were prepared using two different optical centrifuge traps, one with the full spectral bandwidth of the optical centrifuge pulses, and one with reduced bandwidth. The relaxation kinetics of the high-J tail of the inverted distribution from each optical trap was determined based on high-resolution transient IR absorption measurements. In parallel studies, master equation simulations were performed using state-to-state rate constants for CO–CO collisions in states up to J = 90, based on data from double-resonance experiments for CO with J = 0–29 and a fit to a statistical power exponential gap model. The model is in qualitative agreement with the observed relaxation profiles, but the observed decay rate constants are smaller than the simulated values by as much as a factor of 10. The observed decay rate constants also have a stronger J-dependence than predicted by the model. The results are discussed in terms of angular momentum and energy conservation, and compared to the observed orientational anisotropy decay kinetics of optically centrifuged CO molecules. Models for rotational energy transfer could be improved by including angular momentum effects.