波包的空时演化与能级免交叉

Spatial-Temporal Evolution of the Wave Packet and Avoided Level Crossing

采用二维谐振子相干态为初始态 ,在形变原子核系统分别为规则和混沌两种情况下 ,对其在相空间中的时间行为进行了傅里叶分析 ,特别比较了混沌系统中波包宽度在整个时间段与达到饱和后两个阶段的傅里叶分析结果 .指出系统的混沌运动是由于大量能级免交叉的出现在波包运动的初始阶段就破坏了波包内部的规则结构 ,波包各成分间的协同性被破坏 ,波包的运动成为混沌 .此后 ,波包内各成分对波包运动的贡献开始相同 。

In the two cases that the deformed nuclear system is regular and chaotic, the spatial temporal evolution of the coherent states of a two dimensional harmonic oscillator system as an initial state was analyzed with the Fourier transformation, especially by comparing the Fourier transformation of the width of the wave packet in the whole time stage with that the wave packet approaching to the saturation in the chaotic system. It was found that since a large number of avoided level crossings destroy the regular structure of the state space of the system, the components in the wave packet are no longer coherent and the motion of the wave packet becomes chaotic. Afterwards, the contribution coming from the different components tends to uniform, the influence of the avoided level crossings on the motion of the wave packet is not obvious also