Initial State Dependence of Collisional Energy Transfer in Excited DilithiumNeon
Abstract
We have investigated collision induced rotational and vibrational energy transfer in the Li_2 ^* Ne system. Our experiments were performed under singlecollision conditions at an effective temperature of 691K^circ using dispersed, spontaneous, fluorescence techniques. We studied the Li _2 molecules at ten different initial rovibrational levels which covered three different electronic states, A^1Sigma_sp{u }{+}, E^1Sigma _sp{g}{+}, and F ^1Sigma_sp{g}{+} and measured over eight hundred inelastic rate constants. Specifically, for Li_2 A^1Sigma_sp{u}{+ } with an initial rotational level of j _{rm i} = 30, we looked at the initial vibrational level v_{rm i} ranging from 2 to 32 and 2 <= Deltav <= +2. For the Li_2 E ^1Sigma_sp{g}{+} we made measurements for j_{ rm i} = 29, and v_{ rm i} = 4. Finally, for the Li _2 F^1Sigma_sp {g}{+} state, we studied the initial level of j_{rm i} = 31, and v_{rm i} = 10. The dependence of collisional energy transfer on initial vibrational levels is studied systematically in our Li^2 A^1Sigma _sp{u}{+} experiments. We find that increasing v_{rm i } results in a linear increase in the vibrational rate constants, which is accompanied by a decrease in the rotationally inelastic rate constant. The total inelastic rate constant increases with v_{rm i} only at the highest values of v _{rm i}. The net vibrational energy transfer, DeltaE, calculated using rotationally summed rate constants is consistent with a simple model. However, explicit inclusion of rotation gives quite different values of DeltaE. We also compare our experimental results with threedimensional trajectory calculations using both an ab initio potential surface and a simple repulsive potential surface. The measured rate constant distributions as functions of the final rotational level j_{rm f} from electronic states A^1 Sigma_sp{u}{+}, E^1Sigma_sp{g}{+ }, and F^1Sigma_sp {u}{+} are compared. We find that the distribution of vibrationallyelastic rate constants have a wider spread with respect to j_{ rm f} in the Li_2 A^1Sigma_sp{u}{+ } state than in the Li_2 E^1Sigma_sp{g}{+ } or F^1Sigma_sp {g}{+} states. The vibrationally inelastic rate constant distributions for the three different electronic states are very similar.
 Publication:

Ph.D. Thesis
 Pub Date:
 1996
 Bibcode:
 1996PhDT........30G
 Keywords:

 VIBRATION;
 LITHIUM;
 Physics: Atomic; Physics: Molecular