We study the bound state condition for two phonons in the response function appropriate to second order Raman scattering in a zig-zag chain. Using a potential appropriate to polyethylene we find that a bound state exists just above the maximum in the two phonon spectrum. The binding energy is, however, extremely small (0̌.05cm-1).
Bibliographical noteFunding Information:
Eupported in part by a grant from the University of Mmnesota Gradoate school. *Present Address: Honeywell Inc., 5 dt KC, MN t7-2340,260O Ridgway Parkway, Mpls., Mn. 55413.