NCCN-H2碰撞的4D潜在能量表面:在星际温度下p-H2和o-H2的旋转动力学
Apoorv Kushwaha1, T J Dhilip Kumar1
1Quantum Dynamics Lab, Department of Chemistry Indian Institute of Technology Ropar, Rupnagar 140001, India.
The Journal of chemical physics
|August 21, 2023
概括
这项研究计算了NCCN与 (H2) 分子相碰撞的旋转激发率. 奥托-H2 (o-H2) 碰撞的发生率高于对H2 (p-H2) 碰撞的发生率,其近似值与准确计算有很大差异.
科学领域:
- 化学物理 化学物理
- 星际化学 星际化学
- 量子动力学 量子动力学是什么?
背景情况:
- 旋转激发率对于理解星际介质中的分子群体至关重要.
- 之前的研究经常近似对H2 (p-H2) 碰撞或使用简化的相互作用潜力.
- 准确的计算需要详细的潜在能量表面和复杂的动态方法.
研究的目的:
- 为了计算NCCN与para-H2 (p-H2) 和ortho-H2 (o-H2) 碰撞的精确旋转激发率.
- 为了比较使用新的4D初始潜在能量表面 (PES) 获得的结果与以前的近似值.
- 评估近似方法的可靠性,例如合状态/离心器突然计算.
主要方法:
- 一个4D ab initio潜在能量表面 (PES) 是使用CCSD(T) -F12b/AVTZ.开发的.
- 通过使用人工神经网络 (NN) 来增强和安装PES.
- 对横截面进行了密切合 (CC) 计算,并使用波尔兹曼分布推导了直至100K的速率.
主要成果:
- 奥托-H2 (o-H2) 的碰撞率明显高于对H2 (p-H2) 的碰撞率,特别是在更高的旋转转移 (Δj) 时.
- 在 Δj=2 的情况下,o-H2 速率超过p-H2 速率25%-30%,而在较高的转换过程中则超过10-20%.
- 与CC结果相比,合状态/离心器突然近似结果显示了高达40%的偏差.
结论:
- 该研究提供了精确的NCCN-H2旋转激发率,这对于天体化学模型至关重要.
- 开发的4D PES和NN配套方法为未来的计算提供了可靠的方法.
- 对于定量预测,近似方法是不可靠的,这凸显了需要准确的动态计算的需要.
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