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北京化工大学 量子力学 2014年硕士研究生考研真题

北京化工大学 量子力学 2014年硕士研究生考研真题
北京化工大学 量子力学 2014年硕士研究生考研真题

北京大学量子力学教材 第四章

第四章 量子力学中的力学量

第四章目录 §4.1表示力学量算符的性质 (3) (1) 一般运算规则 (3) (2) 算符的对易性 (5) (3) 算符的厄密性(Hermiticity) (7) §4.2 厄密算符的本征值和本征函数 (10) (1) 厄密算符的本征值和本征函数 (10) (2) 厄密算符的本征值的本征函数性质 (12) §4.3 连续谱本征函数“归一化” (15) (1) 连续谱本征函数“归一化” (15) (2) δ函数 (18) (3) 本征函数的封闭性 (22) §4.4 算符的共同本征函数 (24) (1) 算符“涨落”之间的关系 (24) (2) 算符的共同本征函数组 (27) (3) 角动量的共同本征函数组―球谐函数 (28) (4) 力学量的完全集 (34) §4.5 力学量平均值随时间的变化,运动常数(守恒量),恩费斯脱定理(Ehrenfest Theorem) .36 (1) 力学量的平均值,随时间变化;运动常数 (36) (2) Vivial Theorem维里定理 (37) (3) 能量—时间测不准关系 (38) (4) 恩费斯脱定理(Ehrenfest Theorem) (38)

第四章 量子力学中的力学量 §4.1表示力学量算符的性质 (1) 一般运算规则 一个力学量如以算符O ?表示。它代表一运算,它作用于一个波函数时,将其变为另一波函数 )z ,y ,x ()z ,y ,x (O ??=ψ。 它代表一个变换,是将空间分布的几率振幅从 )z ,y ,x ()z ,y ,x (O ???→?ψ 例: /p ?ia x e O ?-=,于是 )x (e )x (O ?dx d a ψ=ψ- ∑∞ =ψ-=0n n n n )x (dx d !n )a ( )a x (-ψ= )x (?= 即将体系的几率分布沿x 方向移动距离a . A. 力学量算符至少是线性算符;量子力学方程是线性齐次方程。 由于态叠加原理,所以在量子力学中的算符应是线性算符。所谓线性算符,即 ψ=ψO ?c )c (O ? 22112211ψ+ψ=ψ+ψO ?c O ?c )c c (O ? 例如1: ψ=?ψ?H ? t i 若1ψ是方程解,2ψ也是方程解,则2211c c ψψ+是体系的可能解。事实上

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