Kinetics of interaction of vibrationally excited OH(X²π_i)_v=9 with simple hydrocarbons at room temperature

Abstract

Relative rate constants for the removal of vibrationally excited OH in the ninth vibrational level of its ground electronic state [designated hereafter by OH'(9)I by interaction with a series of simple hydrocarbons at room temperature are reported. The reaction of hydrogen atoms with ozone was used to generate OH'(9) in a fast flow discharge system at 1.1 2 0.1 torr total pressure. The decrease in the (9 + 3 band) Meinel band chemiluminescent emission intensity at 626 nm was followed as a function of the concentration of added organic or of a reference deactivator (02), respectively, at a fixed reaction time; these data gave relative rate constants, k f / k ; * , for the removal of OH'(9) by the organic. The relative rate constants determined in this study are as follows: C,H,, 2.7 k 0.2; C,H8, 4.4 k 0.4; n-C,H,,, 7.5 t 0.6; iso-C,H,,, 7.3 k 0.8; n--C,H,,, 10.4 2 0.7; C2Ha, 22.9 2 1.8; C3H6, 43.4 k 1.4; cis-2-C4H,, 47.7 2 3.1; C6&, 29 2 7. (Errors are two standard deviations of the weighted mean of experiments in two flow tubes with different wall coatings and carrier gases.) The implications of the trends in these rate constants for the relative contributions of energy transfer and reaction to the net removal of OH'(9) are discussed.