Theoretical Division (T-1, MS B221), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
J Chem Phys. 2018 Jan 28;148(4):044116. doi: 10.1063/1.5014989.
A new electronically non-adiabatic quantum reactive scattering methodology is presented based on a time-independent coupled channel formalism and the adiabatically adjusting principal axis hyperspherical coordinates of T Pack and Parker [J. Chem. Phys. 87, 3888 (1987)]. The methodology computes the full state-to-state scattering matrix for A + B(v, j) ↔ AB(v', j') + B and A + AB(v, j) → A + AB(v', j') reactions that involve two coupled electronic states which exhibit a conical intersection. The methodology accurately treats all six degrees of freedom relative to the center-of-mass which includes non-zero total angular momentum J and identical particle exchange symmetry. The new methodology is applied to the ultracold hydrogen exchange reaction for which large geometric phase effects have been recently reported [B. K. Kendrick et al., Phys. Rev. Lett. 115, 153201 (2015)]. Rate coefficients for the H/D + HD(v = 4, j = 0) → H/D + HD(v', j') reactions are reported for collision energies between 1 μK and 100 K (total energy ≈1.9 eV). A new diabatic potential energy matrix is developed based on the Boothroyd, Keogh, Martin, and Peterson (BKMP2) and double many body expansion plus single-polynomial (DSP) adiabatic potential energy surfaces for the ground and first excited electronic states of H, respectively. The rate coefficients computed using the new non-adiabatic methodology and diabatic potential matrix reproduce the recently reported rates that include the geometric phase and are computed using a single adiabatic ground electronic state potential energy surface (BKMP2). The dramatic enhancement and suppression of the ultracold rates due to the geometric phase are confirmed as well as its effects on several shape resonances near 1 K. The results reported here represent the first fully non-adiabatic quantum reactive scattering calculation for an ultracold reaction and validate the importance of the geometric phase on the Wigner threshold behavior.
一种新的非绝热量子散射方法，基于时间独立的耦合通道理论和 T Pack 和 Parker 的绝热调整主轴超球坐标 [J. Chem. Phys. 87, 3888 (1987)]。该方法计算了 A + B(v, j) ↔ AB(v', j') + B 和 A + AB(v, j) → A + AB(v', j') 反应的全态态散射矩阵，其中涉及两个耦合电子态，它们表现出锥形交叉。该方法准确地处理了相对于质心的所有六个自由度，包括非零总角动量 J 和相同粒子交换对称性。新方法应用于最近报道的超冷氢交换反应 [B. K. Kendrick 等人，Phys. Rev. Lett. 115, 153201 (2015)]。报道了碰撞能在 1 μK 和 100 K 之间的 H/D + HD(v = 4, j = 0) → H/D + HD(v', j') 反应的速率系数（总能量约为 1.9 eV）。根据 Boothroyd、Keogh、Martin 和 Peterson (BKMP2) 和双多体展开加单多项式 (DSP) 绝热势能面，为 H 的基态和第一激发电子态分别开发了新的非绝热势能矩阵。使用新的非绝热方法和非绝热势能矩阵计算的速率系数重现了最近报道的速率，其中包括几何相位，并使用单一绝热基态电子势能面 (BKMP2) 计算。还证实了几何相位对超冷速率的显著增强和抑制，以及它对 1 K 附近几个形状共振的影响。这里报告的结果代表了第一个超冷反应的完全非绝热量子散射计算，并验证了几何相位对 Wigner 阈值行为的重要性。
