Laser fluorescence study of the Pb+F2, Cl2 reactions: Internal state distribution of the PbCl product and radiative lifetimes of PbF(A,B) and PbCl(A)

Abstract

The reactions of Pb atoms with molecular reagents F2 and Cl2 have been studied in a molecular beam apparatus by laser fluorescence detection of PbF and PbCl products. The experiments were performed in a beam-gas configuration under single-collision conditions. The PbCl product from Pb+Cl2 was observed in the vibrational levels v≤17 of the ground X1 electronic state. The PbCl product vibrational state distribution was derived; the average vibrational excitation was found to be 21% of the total available energy. For Pb+F2, PbF(X1) product was detected in only the v=0 and 1 vibrational levels, and the rovibrational state distribution could be characterized by a 300 K Boltzmann distribution. By modulating the Pb beam, it was concluded that this observed product was an artifact and did not arise from bimolecular gas-phase collisions. The radiative lifetimes of the PbF(A,B) and PbCl(A) states were also measured and were found to equal 4.9±0.3 μs, <10 ns, and 1.14±0.06 μs, respectively, averaged over the observed vibrational levels.