A modified Gaussian wave packet relaxation method is proposed to calculate the ground state wave function using an expansion of frozen Gaussian wave packets. This new procedure consists of two steps. In the first step, a multidimensional Gaussian product placed at the ground state equilibrium geometry is propagated in imaginary time. The relaxation optimizes the widths of the one-dimensional Gaussians. In the second step, additional Gaussian wave packets with the same widths are placed near the equilibrium geometry, and the corresponding expansion coefficients are optimized using the same relaxation method. This new algorithm is tested in photodissociation of NOCl and NH₃, and the results show good agreement with the exact results in the energy, wave function, and absorption spectrum. In particular, the highly structured absorption spectrum of NH₃ is reproduced, underscoring the accuracy of both the initial wave packet and the excited state propagation.

中文翻译：

---

修正高斯波包方法计算光解离中的初始状态波函数

提出了一种改进的高斯波包弛豫方法，利用冻结的高斯波包的展开来计算基态波函数。此新过程包括两个步骤。第一步，在假想时间内传播处于基态平衡几何的多维高斯积。弛豫优化了一维高斯的宽度。在第二步中，将具有相同宽度的其他高斯波包放在平衡几何体附近，并使用相同的松弛方法优化相应的膨胀系数。该新算法已在NOCl和NH _3的光解离中进行了测试，结果与能量，波函数和吸收光谱的精确结果吻合良好。特别地，再现了高度结构化的NH ₃吸收光谱，强调了初始波包和激发态传播的准确性。