This is a study of the deexcitation mechanisms of the metastable 52D3/2 state of Ba+ in about I atm He buffer gas in the temperature range of 500-650 deg C.The ions were produced by three- photon ionization with light tuned to a resonance between two excited states of Ba, enabling the electron density to be varied independently of the temperature and pressure.The deexcitation is dominated by superelastic scattering of electrons with a cross section of ?se = 45 + 20 A2 (corresponding to an electron-impact excitation cross section of 11 A2 ) and quenching by Ba atoms with a cross section of ?Ba = 130 +/- 25 Angstroem2.No dependence of the deexcitation rate on He density was detected, and we infer an upper limit on the cross section of sHe9*10-22 cm2.
Wave packet dynamics on the repulsive potential surface of BaFCH3 excited at 745 nm
We studied the time evolution of the wave packet formed by the excitation of the Ba?FCH3 complex with a 120 fs laser pulse at 745 nm to its electronic ?' state which is repulsive at the ground state geometry and decays to Ba and CH3F fragments. By applying probe pulses with different wavelengths of 400 and 267 nm, respectively, we observed strongly different time dependences of the pump-probe signals for the BaF+ and Ba+ ions determined by the Franck-Condon windows available in both cases. The experimental results are qualitatively confirmed by theoretical studies based on ab initio calculations of the corresponding potential energy surfaces.