Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
J Chem Phys. 2012 Sep 14;137(10):104301. doi: 10.1063/1.4750029.
Radiative association of silicon mononitride (SiN) in its two lowest molecular electronic states is studied through quantum and classical dynamics. Special attention is paid to the behavior of the cross section at high collision energies. A modified expression for the semiclassical cross section is presented which excludes transitions to continuum states. This gives improved agreement with quantum mechanical perturbation theory at high energies. The high energy cross section is overestimated if conventional semiclassical theory is used. The modified semiclassical theory should be valid in general for radiative association transitions from an upper to a lower electronic state. We also implement a quantum dynamical optical potential method with the same type of modification. The rate coefficient is calculated using Breit-Wigner theory and the modified semiclassical formula for the resonance and direct contributions, respectively, for temperatures from 10 K to 20,000 K. A rapid decrease in the rate constant for formation of ground state SiN is observed above 2000 K which was not seen previously.
通过量子和经典动力学研究了硅单氮化物 (SiN) 在其两个最低分子电子态下的辐射缔合。特别关注高碰撞能下截面的行为。提出了一种修正的半经典截面表达式，该表达式排除了向连续态的跃迁。这在高能下与量子力学微扰理论有更好的一致性。如果使用传统的半经典理论，高能截面会被高估。这种修正的半经典理论通常适用于从较高电子态到较低电子态的辐射缔合跃迁。我们还实现了一种具有相同类型修正的量子动力学光学势方法。速率系数使用 Breit-Wigner 理论和修正的半经典公式分别计算共振和直接贡献，温度范围从 10 K 到 20,000 K。在 2000 K 以上观察到形成基态 SiN 的速率常数迅速下降，这是以前没有观察到的。
