Yield of excited CO molecules from dissociative recombination of HCO+ and HOC+ ions with electrons.

The authors have investigated CO band emissions arising from the dissociative recombination of HCO(+) and HOC(+) ions with thermal electrons in a flowing afterglow plasma. The quantitative analysis of the band intensities showed that HCO(+) recombination forms the long-lived CO(a (3)Pi) state with a yield of 0.23+/-0.12, while HOC(+) recombination favors formation of CO(a' (3)Sigma(+)) and CO(d (3)Delta) with a combined yield of greater than 0.4. The observed vibrational distribution for the CO(a) state reproduces theoretical predictions quite well. The vibrational distributions for CO(a') and CO(d) are, in part, inverted, presumably as a consequence of a change in CO equilibrium bond length during recombination. The observations are compatible with current knowledge of the potential surfaces of states of HCO and HCO(+).

Yield of electronically excited CN molecules from the dissociative recombination of HNC+ with electrons.

The authors have studied CN(B-X) and CN(A-X) emissions produced by the dissociative recombination of HNC+ ions with thermal electrons in a flowing afterglow experiment. A separate drift tube study showed that the reaction Ar(+)+HCN, the precursor reaction used in the flow-tube experiment, produces predominantly HNC+ rather than the more energetic HCN+ isomer. Models simulating the ion-chemical processes, diffusion, and gas mixing in the afterglow plasma were fitted to observed position dependent CN(A-X) and CN(B-X) band intensities. Absolute yields of CN(B) and CN(A) were then obtained by comparing the CN band intensities to those of CO bands produced by recombination of CO(2) (+) ions. It was concluded that the 300 K recombination coefficient of HNC+ is close to 2 x 10(-7) cm(3) s(-1), that CN(B) is formed with a yield of 0.22+/-0.08 and CN(A) with a yield of 0.14+/-0.05. By comparison to synthetic spectra, the rotational temperature of CN(B) was estimated to be approximately 2500 K. It was also found that recombination produces CN(B) and CN(A) with far greater vibrational excitation than would be expected from the "impulse model" of Bates [Mon. Not. R. Astron. Soc. 263, 369 (1993)].

Yield of electronically excited N2 molecules from the dissociative recombination of N2H+ with e-.

Quantitative spectroscopic observations of the N2 first positive band system (N2(B 3Pig-A 3Sigmau+))/electron in a recombining N2H+ flowing-afterglow plasma indicate that a substantial fraction of the product N2 molecules are formed in one or more of the low-lying triplet states, B 3Pig, A 3Sigmau+, and W 3Deltau. The total measured N2(B-A) emission intensity from N2(B,v' > or = 1) is equivalent to a yield of (19 +/- 8)%. The effect of rapid collision-induced transitions between states of the triplet manifold is discussed..