Principles of Quantum Mechanics · Problem 18.7

Time-Dependent Perturbation Theory — R. Shankar

Physics — Quantum Mechanics · time-dependent-perturbation-theory

Problem

A particle starts out (t=0t = 0) in the NN-th state of the infinite square well. Now the "floor" of the well rises suddenly by an amount V0V_0 (that is, H′=V0H' = V_0, for 0<x<a0 < x < a, and zero outside); after a time TT the perturbation is removed. (a) In first-order perturbation theory, what is the probability that the particle is now in the nn-th state (in terms of nn, NN, V0V_0, aa, TT, ℏ\hbar, and the energies EnE_n)? Note that there are actually two cases: n=Nn = N and n≠Nn \neq N. (b) Can this system make a transition to any other state? Explain.

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