Relaxation rates for 02('&+) by nonradiative pathways have been determined using the fast-flow technique. 02 ('\3,+) is formed from 0 2 ( l A g ! by an energy pooling process. 02('AK) is generated by passing purified oxygen through a microwave discharge. Oxygen atoms are removed by distilling mercury vapor through the discharge zone. It has been observed that the wall loss rate for 02('Z,+) decreases with increasing pressure of oxygen and thus appears to be diffusion controlled. Quenching rate constants for 0 2 , N2. and He have been determined and found to be (1.5 f 0.1) X lo4, (1.0 f 0.05) X lo6 and (1.2 f 0.1) X lo5 I./mol-sec, respectively.
The rate constants for the quenching of O,('Ag) with carbon disulfide, dimethyl sulfide, dimethyl disulfide, diallyl disulfide, ethyl mercaptan, and thiophene have been determined in a discharge flow system in the absence of oxygen atoms. The rate constants are found to be (6.5 2 0.6) x lo4, (1.8 2 0.2) x lo4, and (3.5 -t 0.6) x lo3 L/mol . s for dimethyl sulfide, ethyl mercaptan, and thiophene, respectively. The other compounds have rate constants ~9 . 9 x 10, L/mol . s. In the case of dimethyl sulfide, even when NO, concentration is more than what is required to remove oxygen atoms completely, the rate constants are found to vary with different amounts of NO,. No correlation is found to exist between the logarithm of the rate constants and the ionization potentials of the compounds.
. Can. J. Chem. 62, 417 (1984). Emissions from excited SO2 in its singlet state ('B, and/or 'A,) and triplet state ('B,) have been observed in gas-phase chemiluminescent reactions of ozone with a number of sulphur compounds. The compounds studied are carbon disulphide, thiophene, diallyl sulphide, diallyl disulphide, dimethyl sulphide, dimethyl disulphide, and thiophenol. The reaction pathways responsible for the formation of excited molecules are discussed. The remarkable similarity between the emission spectra of the reactions and the chemiluminescence from the SO + O3 reaction confirms that SO is a precursor for the observed chemiluminescence. Disulphides are found to be more chemiluminescent than monosulphides. The absence of chemiluminescence from HCHO* in the reactions of ozone with allyl sulphide and disulphide indicates that the attack of ozone molecule is on the C-S bond in organic sulphides. [Traduit par le journal]
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