REACTION OF NH(A(1)DELTA) WITH SIH4 - COMPARISON WITH CH4 AND C3H8

By using a laser induced fluorescence technique, the reactions of NH with SiH4, CH4, and C3H8 are investigated. From the first-order decay rates of NH(a(1) Delta, X(3) Sigma(-)), the rate constants are determined to be k(1) (1.36 +/- 0.02) x 10(-10), k(2) < 10(-13), and k(3) = (3.26 +/- 0.17) x 10(-12) (cm(3) molecule(-1) s(-1)) for the reactions NH(a) + SiH4 (1), NH(X) + SiH4 (2), and NH(a) + CH4 (3), respectively. By calibrating the LIF intensities of NH2 and H vs NH(a) using the reaction NH(a) + H-2 --> NH2 + H, product branching fractions for the above reactions are determined; that is, the yields of NH2 are found to be 0.39 +/- 0.07, 0.86 +/- 0.10, and 0.20 +/- 0.05 for reactions 1, 3, and NH(a) + C3H8 (4), respectively. The yield of H atoms is concluded to be minor, and quenching of NH(a) is found to be negligibly slow in all these reactions. Time-resolved mass spectrometric measurements indicate that the main product of reaction 1 is H-2.