title: Collisional deactivation of Ba 5d7p (3)D1 by noble gases.
abstract: Collisional deactivation of the 5d7p (3)D1 state of Ba by noble gases is studied by time- and wavelength-resolved fluorescence techniques. A pulsed, frequency-doubled dye laser at 273.9 nm excites the 5d7p (3)D1 level from the ground state, and fluorescence at 364.1 and 366.6 nm from the 5d7p (3)D1 --> 6s5d (3)D1 and 5d7p (3)D1 --> 6s5d (3)D2 transitions, respectively, is monitored in real time to obtain the deactivation rate constants. At 835 K these rate constants are as follows: He, (1.69 +/- 0.08) x 10(-9) cm(3) s(-1); Ne, (3.93 +/- 0.14) x 10(-10) cm(3) s(-1); Ar, (4.53 +/- 0.15) x 10(-10) cm(3) s(-1); Kr, (4.64 +/- 0.13) x 10(-10) cm(3) s(-1); Xe, (5.59 +/- 0.22) x 10(-10) cm(3) s(-1). From time-resolved 5d7p (3)D1 emission in the absence of noble gas and from the intercepts of the quenching plots, the lifetime of this state is determined to be 100 +/- 1 ns. Using time- and wavelength-resolved Ba emission with a low background pressure of noble gas, radiative lifetimes of several near-resonant states are determined from the exponential rise of the fluorescence signals. These results are as follows: 5d6d (3)D3, 28 +/- 3 ns; 5d7p (3)P1, 46 +/- 2 ns; 5d6d (3)G3, 21.5 +/- 0.8 ns; 5d7p (3)F3, 48 +/- 1 ns. Integrated fluorescence signals are used to infer the relative rate constants for population transfer from the 5d7p (3)D1 state to eleven near-resonant fine structure states.
authors.affiliation: Department of Physics and Astronomy, 44 Campus Avenue, Bates College, Lewiston, Maine 04240-6084, USA. jsmedley@bates.edu
authors.forename: John E
authors.initials: JE
authors.lastname: Smedley
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Coulter
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Felton
authors.forename: Kayla S
authors.initials: KS
authors.lastname: Zomlefer
mesh_terms: D001464:Barium / Q000737:chemistry*; D004735:Energy Transfer; D005453:Fluorescence; D008956:Models, Chemical; D005741:Noble Gases / Q000737:chemistry*; D013997:Time Factors
chemical_list: D005741:Noble Gases; D001464:Barium