OBSERVATION OF THE $2^{3}\Sigma^{+}_{g}-1^{3}\Sigma^{+}_{u}$ and $1^{3}\Pi_{g}-1^{3}\Sigma^{+}_{u}$ TRANSITIONS OF THE TRIPLET NaK MOLECULE ON THE SURFACE OF HELIUM CLUSTERS

$^{1}$ W.J. Stevens, D.D. Konowalow, and Lyn B. Ratchiff, J. Chem. Phys. 80, 1215 (1984). $^{2}$ G.H. Jeung, J.P. Daudey, and J. P. Malricu, Chem. Phys. Lett. 94, 300 (1983). $^{3}$ W.P. Kowalczyk and N. Sadeghi, J. Chem. Phys. 102, 8321 (1995).Author Institution: Department of Chemistry, Princeton UniversityHigh spin (triplet) NaK dimers have been successfully prepared on the surface of helium clusters through a pick-up process in which a He cluster beam passes through two independent alkali pick-up cells, each containing an alkali vapor at pressures around $10^{2}$ Pa. Excitiation and emission spectra have been recorded for both the $2^{3}\Sigma^{+}_{g}-1^{3}\Sigma^{+}_{u}$ and $1^{3}\Pi_{g}-1^{3}\Sigma^{+}_{u}$ transitions. Comparisions of the experimental spectra with the theoretical calculations of Stevens et al.$1^{3}\Pi_{g}$ and of Jeung et $al.^{2}$ have been made obtaining information on the potenntial of the upper $1^{3}\Pi_{g}$ state. Similar comparisons with the work of Kowalczyk et $al.^{3}$ have made for the $2^{3}\Sigma^{+}_{g}-1^{3}\Sigma^{+}_{u}$ transition. Several different emission channels have beeen detected for each system following excitation, including atomic fluorescence and non-adiabatic corssings into the singlet manifold of the dimer. The emission spectra provide evidence of vibrational relaxation of the dimer on the He surface occuring on a time scale shorter than that of the molecular fluorescence