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Kinetic investigation of the molecular chemiluminescence SrBr(A 2 II, B 2 Σ + → X 2 Σ + ) and the time-resolved atomic fluorescence Sr(5 3 P 1 → 5 1 S 0 ) following the pulsed dye-laser generation of Sr(5 3 P J in the presence of CH 3 Br and CF 3 Br

Journal of Photochemistry and Photobiology A: Chemistry, ISSN: 1010-6030, Vol: 83, Issue: 2, Page: 79-89
1994
  • 11
    Citations
  • 0
    Usage
  • 3
    Captures
  • 0
    Mentions
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    11
    • Citation Indexes
      11
  • Captures
    3

Article Description

A kinetic study is presented of the vibronic energy distribution in SrBr following the reactions of the optically metastable, electronically excited strontium atom, Sr(5s5p( 3 P J )), 1.807 eV above its 5s 2 ( 1 S 0 electronic ground state, in the presence of CH 3 Br and CF 3 Br. Sr(5 3 P 1 ) was generated by pulsed dye-laser excitation of ground-state strontium vapour at λ=689.3 nm (Sr(5 3 P 1 ←5 1 S 0 )) at elevated temperature (850 K) in the presence of excess helium buffer gas in a slow flow system, kinetically equivalent to a static system. The decay of Sr(5 3 P J ) is then monitored by time-resolved atomic fluorescence from Sr(5 3 P 1 ) at the resonance wavelength following rapid Boltzmann equilibration within the 3 P J spin-orbit manifold using boxcar integration. Time-resolved molecular chemiluminescence to the ground state was also observed from electronically excited strontium bromide and investigated in detail via the SrBr(A 2 Π sol:32 → X 2 Σ + (Δν=0, λ≈667 nm) and SrBr(B 2 Σ + → X 2 Σ + ) (Δν=0, λ≈651 nm) systems. The A 2 Π (177.6 kJ mol −1 and B 2 Σ + (183.6 kJ mol −1 ) states of SrBr are both energetically accessible on collision between Sr( 3 P) and CH 3 Br and CF 3 Br. Both the atomic and molecular (A,B,–X) chemiluminescence emissions are shown to be exponential in form with both reactants and characterized by first-order decay coefficients which are found to be equal under identical conditions within experimental error. SrBr(A 2 Π) and SrBr(B 2 Σ + are thus shown to arise from direct reaction with both CH 3 Br and CF 3 Br. The results obtained here in the time domain are compared with analogous chemiluminescence studies on Sr( 3 P) with halides, including bromides, using molecular beams and with previous time-resolved measurements on SrCl(A 3 II, B 2 Σ + X 2 Σ + ) that we have reported. The results are also compared with those from a series of investigations we have presented from time-domain investigations of molecular emissions from CaF, Cl, Br, I (A,B–X) arising from the collisions of Ca(4 3 P J ) with appropriate halides.

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