TWO PHOTON EXCITATION OF THE $D^{1}\Delta - X^{1}\Sigma^{+}$ TRANSITION IN CO

Author Institution: Department of Chemistry, Massachusetts Institute of Technology Cambridge; Physical Chemistry Laboratory, Oxford University; Materials and Molecular Research, Division Lawrence Berkeley Laboratory and Department of Chemistry University of California; Department of Chemistry, Massachusetts Institute of Technology CambridgeA frequency doubled pulsed dye laser is used to promote two-photon excitation of the $D^{1}\Delta - X^{1}\Sigma^{+}$ transition in carbon monoxide. Collisional transfer to $A^{1}\Pi$ leads to ultraviolet fluorescence which is detected with a solar blind photomultiplier. Rotationally resolved structure belonging to bands of three isotopically substituted molecules has been measured relative to the visible spectrum of iodine. Several vibrational bands up to $v^{\prime} = 12$ have been analyzed and these data, combined with Simmons and Tilford’s$^{1}$ values for $v^{\prime} = 1$, give the molecular constants. Preliminary values for $^{12}CO$ are: $T_{e} = 65,975.8(5); \omega_{e} = 1061.7(3); \omega_{e}x_{e} = 9.86(4); B_{e} = 1.259(4); D_{e} = 7\times10^{-6} \alpha_{e} = .018(1)$ (all $cm^{-1}$). $^{1}$J.D. Simmons and S.G. Tilford, J. Chem. Phys. 45, 2965 (1966)