Subject: What is EXACTLY a "resonance"?

From: [email-masked] (Dario Bressanini)
Date: Tue, 21 Jan 1997 08:28:23 +0100

Dear CCLers,

What is EXACTLY a "resonance"? Is it correct to say that
it is a  discrete level of an Hamiltonian embedded in the continuum?
By discrete level i mean a stationary state, an eigenfuction belonging
to the discrete spectrum of the hamiltonian, a square integrable function.can someone  suggest a recent review/article on the subject?
thanks  Dario Bressanini   [email-masked]

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From: "John-M. Sichel" <[email-masked]>
Date: Tue, 21 Jan 1997 10:20:18 -0300 (ADT)

> thanks  Dario Bressanini   [email-masked]

A resonance is _approximately_ a discrete state, but it does interact 
(perhaps weakly) with the continuum states at nearby energies. The exact 
states _near_ the resonance energy therefore have some discrete character 
which makes them different from continuum states at other energies. For 
example, if absorption to the discrete state is allowed, there will be 
enhanced absorption to states in this energy region. The observed effect 
will then be a peak or "resonance" near the energy of the discrete state.

     John-M. Sichel
     Dept. de chimie et biochimie
     Universite de Moncton
     Moncton NB, Canada    
     E1A 3E9

     Tel: (506-)858-4313       E-mail: [email-masked]

I know you believe you understand what you think I said, but I am not sure
you realize that what you heard is not what I meant. (Gaussian92)