Kinetics of formation and quenching of 5s 4 P 5/2, ? Br excited atoms using fluorescence spectrometry

Abstract
Vacuum ultraviolet photolysis of Br2 was shown to form excited Br 5s4P5/2 and 4P atoms by independent primary processes. The quenching of atomic fluorescence emitted by the excited Br atoms has been studied in a flow system at 298 K, in which the steady state concentration of ground state Br 4p5 2P was less than 1010 atom cm–3. Although Br 5s4P atoms have too short a radiative lifetime to show quenching at pressures up to 3 kN m–2, quenching cross sections σM(10–20 m2) were determined for the more metastable Br 5s4P5/2 atoms: σHe < 0.02; σAr < 0.04; σH2 = 0.27; σN2 = 1.8; σCO= 2.9; σSF6 = 28; σBr2 = 146. These quenching cross sections are compared with those for quenching of metastable Br 4p5 2P½ atoms.
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