Collisional Deactivation of O2(1Δg)

Abstract

This paper reports determinations of collisional deactivation rate constants for O2(1Δg) by minor atmospheric constituents and other gases. The benzene–oxygen photochemical system was used to produce O2(1Δg), and relative concentrations were measured by monitoring the intensity of its emission at 1.27 μ. The rate constants for the reaction O2(1Δg)+M→O2+M were 4.53 × 10−18, 5.60 × 10−18, and (0.5–1.0) × 10−19 (cm3 molecule−1·sec−1) for M=H2, H2O, and N2O, respectively. Upper limits were obtained for deactivation by He, Ar, CO2, and SF6 of 8.0 × 10−21, 8.3 × 10−21, 1.5 × 10−20, and 1.2 × 10−20, respectively. The temperature dependence of the deactivation of O2(1Δg) by oxygen has been investigated. The rate constant can be expressed in the form kO2 = 2.22 ± 0.09 × 10−18 (T / 300)n, where n = 0.78 ± 0.32 and T is the temperature in degrees Kelvin.

On the role of excited species in hydrogen combustion

“…Their measurements are in a very good agreement with the results of Chatelet et al [86] and with the rate obtained later by Furui et al [87]. Findlay and Snelling [88] summarized earlier measurements of collisional deactivation of singlet oxygen and concluded that hydrogen-containing species possess efficiencies close to molecular oxygen, which was recently confirmed for hydrogen [89], water [90], and a range of hydrocarbons [91]. This was attributed to weak chemical interaction otherwise manifested in reaction (31) or reaction between O 2 (1 ) and H 2 O discussed in the following.…”

“…Since deactivation of O 2 (1 ) is a spin forbidden process, the rates of quenching by non-reacting species, Ar, He, N 2 and CO 2 , are very small compared to O 2 and hydrogen-containing collision partners. For consistency, all these rates were taken from the work of Findlay and Snelling [88]. The values for N 2 and Ar used in our previous work [34] and based on the measurements of Clark and Wayne [80,92] were apparently overestimated due to experimental problems [81] discussed above in relation to reaction (31).…”

“…In fact, the Arrhenius behavior of collisional quenching should not necessarily be expected; predictions of different models of E-V energy transfer [85,93,94] can be better presented as powerlaw temperature dependences. Findlay and Snelling [88] approximated their measurements with the rate proportional to T 0.78 ± 0.32 , while Popov [28] adopted T 0.5 dependence based on theoretical calculations. One should note that description of the rate constant by T 0.5 dependence does not deviate more than by a factor of 2 from the Arrhenius expression with activation energy of 400 cal/mol [85] over the entire temperature range from room to combustion temperatures.…”

A quasi-static method for measuring the deactivation rate constants of O2(a1Δg) in gas phase by IR radiation decay

“…Experimental investigations on the generation and deactivation of O 2 (a 1 D) have been going on for several decades [1][2][3]. So far, the deactivation rate constants of O 2 (a 1 D) by various gases have been measured by many researchers using different methods [4][5][6][7][8][9][10][11]. However, in these methods the energy-pooling reaction of O 2 (a 1 D) has unfortunately been neglected.…”

The Ultraviolet Flash Photolysis of Ozone and the Reaction of O(1D) with H2O

“…. However, a tenfold increase in k2, and k,, above the lower limits given in Table 2 produced a curve which was almost indistinguishable from that for mechanism (6). Mechanisms (a), (b), and (d), were not sensitive to increases in kz0 and k,,.…”