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Transactions of the Faraday Society


Transactions of the Faraday Society was published from 1905 - 1971.

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Paper

Trans. Faraday Soc. , 1971, 67, 272 - 288, DOI: 10.1039/TF9716700272

Rates of energy transfer from N2A3+u to various molecules. Initial and final quantum states in the transfer to NOX2 and Hg(61S0), and vibrational relaxation of N2A3+u(v= 1) in helium

A. B. Callear and P. M. Wood

A technique of monochromatic flash spectroscopy with the resonance radiations of Xe (1470 Å) and Kr (1236 Å) is described, with a quantal absorption of 1.4 × 1014 quanta cm–3 per pulse. Production and decay of N2A3+u(v= 0,1) was monitored photoelectrically from the sensitized fluorescence of either NO(-bands) or Hg (2537 Å) line. Rate coefficients for deactivation of N2A3+u were recorded as kHg= 2.9 × 10–10; kC2H2= 1.6 × 10–10; kC2H4= 1.1 × 10–10; kNO= 8.0 × 10–11; kNH3 < 2 × 10–11; kN2O= 6.1 × 10–12; kO2= 3.6 × 10–12; kn-C4H10= 2.7 × 10–12; kCO(N*2(v= 0))= 1.5 × 10–12, kCO(N*2(v= 1))= 2.4 × 10–11; kC3H8= 1.3 × 10–12; kC2H6= 3.6 × 10–13; and kH2= 3 × 10–15 cm3 molecule–1 s–1; a significant difference in the rates of deactivation of the v= 0 and 1 states of N2A3+u was found only for CO. Except in the transfer to NH3 and Hg, the measurements agree well with those of Young et al.1–5In high pressures of He, vibrational relaxation of N2A3+u(v= 1) was induced by collision prior to its deactivation, and a rate coefficient of 1.2 × 10–15cm3 molecule –1 s–1 was recorded. Correlation of initial and final quantum states was achieved for the transfer to NO, which populates predominantly A2+(v= 0 and 1) : N2A3+u(v= 0)+ NOX2(v= 0) N2X1+g+ NOA2+(v= 1 : 0 = 1:9·5); N2A3+u(v= 1)+ NOX2(v= 0) N2X1+g+ NOA2+(v= 1:0 = 1:1·9). The results were analyzed with a model in which the transition probabilities are proportional to the products of the two Franck-Condon factors and the mean density of states associated with particular reaction channels. Transfer from N2A3+u to Hg populates directly the Hg(63P0) state to the extent of about 25 %. From a comparison of the simultaneous NO and Hg 2537 Å emissions, it was suggested that excitation of NOA2+ occurs with nearly unit efficiency. Excited atomic iodine (I52P½) was detected, via absorption of the 2060 Å line by kinetic spectroscopy, in the deactivation of N2A3+u by CH3I.