EXPERIMENTAL AND THEORETICAL KINETICS FOR THE REACTION OF AL WITH O-2AT TEMPERATURES BETWEEN 23 AND 295 K

The first study of the kinetics of Al atoms with O-2 at low and ultral ow temperatures is reported. Rate constants have been measured from 29 5 to 23 K using the pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique in a CRESU (Cinetique de Reaction en Ecoulement S upersonique Uniforme) apparatus. Rate constants were found to increase monotonically with decreasing temperature: k(T) = (1.75 +/- 0.10) x 1 0(-10)(T/298)(-0.25+/-0.02) exp[(7.3 +/- 3.0)/T] cm(3) s(-1). The rate constant for the reaction Al with O-2 has also been calculated as a f unction of temperature using a theoretical approach based on the adiab atic capture centrifugal sudden approximation (ACCSA) method, These ca lculations were found to be in good agreement with experimental result s and were able to explain the observed temperature dependence by the open-shell nature of the reactants, Possible astrophysical implication s are also discussed concerning the chemistry of aluminum atoms in the interstellar medium.