An identity-forbidden two-photon transition has been observed for the first time, between the I1- and X1+ states in carbon monoxide. Such transitions are dipole allowed only for the absorption of two photons with different frequencies and polarization states. Only P and R rotational branches of the (7-0) band are observed, and the line intensities are maximized for perpendicular photon polarizations. This is the first experimental demonstration of the two-photon electric-dipole selection rule +-.
ASJC Scopus subject areas
- Physics and Astronomy(all)