harmonic oscillator for triatomic system

From: "Dr. Peter Burger" <chburger -AatT- aci.unizh.ch>
Subject: harmonic oscillator for triatomic system
Date: Mon, 29 Oct 2001 17:45:11 +0100

Dear CCLers,
 embarassing but I dare nevertheless to ask.
 I am looking for an expression of the angle bending term using the
 harmonic oscillator approximation for a triatomic system B-A-C in a form
 as for the bond stretch term in a diatomic system, i.e. nu = 1/2PI
 sqrt(k/mu). In particular, what form does the reduced mass term
 mu have in the triatomic system?
 Best regards,
 Peter