Electric dipole moments of excited vibrational levels in theXtilde;thinsp;1A1state of formaldehyde by stimulated emission spectroscopy

摘要

The electric dipole moments of the 44(E4ngr;4=4628.4 cmminus;1), 2242(E2ngr;22ngr;4)=5770 cmminus;1), and 2144(E1ngr;24ngr;4=6347 cmminus;1) levels of H2CO are measured as 2.2723(86), 2.3222(47), and 2.2825(33) D, respectively. This first combination of stimulated emission pumping (SEP) with a static electric field demonstrates the possibility of systematically measuring dipole moments for highly excited vibrational levels of polyatomic molecules in their electronic ground states. The present dipole moment measurements and all previous ones involving overtones and combinations of the Cndash;O stretch (ngr;2) and outhyphen;ofhyphen;plane bend (ngr;4) are reduced to two types of expansions. The dipole moment mgr; is expressed both as an expansion in the normal coordinate displacements and as an expansion through squared terms in thev2andv4vibrational quantum numbers.