Question in Principles of Quantum Mechanics by Shankar

1. Feb 2, 2012

wbphysics

Hi,
Im studying a book "Principles of Quantum Mechanics" by Shankar.
Im in the fifth chapter, Simple Problems in One dimension.
In page 169 to 170,
the book says about the standard procedure for finding the fate of the incident wave packet.
But i dont understand why we are finding a(E)=<ψ_E/ψ_I> , ψ_E is a normalized eigenfunction of Hamiltonian and ψ_I is an incident wave packet.
More over, in page 170, Step2, Calculating a(E),
it says a part of integral vanishes since, ψ_I in k space is peaked around k=k_0 and is orthogonal to negative momentum states. (k_0=p_0/h bar)