Use of local modes in the description of highly vibrationally excited molecules
Use of local modes in the description of highly vibrationally excited molecules
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使用局部模式来描述高度振动激发的分子
DOI：
10.1021/ar50114a003
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发表时间：
1977
影响因子：
18.3
通讯作者：
B. Henry
中科院分区：
文献类型：
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作者：
B. Henry
Crawford和Ov-erend的一部电影很好地证明了简正振动模的存在。1一个松散耦合的偏心马达激励二氧化碳分子的球和弹簧模型。随着电机旋转频率的增加，被激发的“原子”的混沌运动被分解为相干的弯曲运动。电机频率的进一步提高再次导致混沌，直到在某个更高的频率出现对称拉伸运动，最后在更高的频率出现反对称拉伸。因此，我们直接看到在这些“自然”频率下，“分子”中的每个“原子”以相同的频率和相位运动，使得每个“原子”同时达到其最大位移位置，并且每个“原子”同时通过其平衡位置。这些是简正模的常见特征，它们解析地产生于多原子分子中的振动遵循简谐力定律的假设。在简谐近似(方程1)中，势能和动能都是对角的，沿着发生简正模运动的法坐标Qi。因此，分子可以
The existence of normal modes of vibration is ele-gantly demonstrated in a film by Crawford andOv-erend. 1 A loosely coupled eccentric motor excites a ball and spring model of the carbon dioxide molecule. As the frequency of rotation of the motor increases, the chaotic motions of the excited “atoms” are resolved into a coherent bending motion. A further increase in the frequency of the motor again procedures chaos until, at some higher frequency, the symmetric stretching motion appears and finally, at even higher frequency, the antisymmetric stretch. Thus we see directly that at these “natural” frequencies each “atom” inthe “molecule” is moving with the same frequency and phase so that each “atom” reaches its position of maximum displacement at the same time and each “atom” passes through its equilibrium position at the same time.These are the familar characteristics of normal modes and they arise analytically from the assumption that vibrational motion in polyatomic molecules follows a harmonic forcelaw. In terms of the normal coordinates, Qi, along which normal-mode motion occurs, both the potential and kinetic energies are diagonal in the harmonic approximation (eq 1). Thus the molecule can