Complete falloff curves for the unimolecular decomposition of i-propoxy radicals between 330 and 408 K

The temperature and pressure dependence of the rate constant for the unimol ecular decomposition of i-propoxy radicals has been determined using the la ser photolysis/laser induced fluorescence technique. Important features of the potential energy surface have been calculated by nb initio methods. Exp eriments have been performed at total pressures between 0.01 and 60 bar of helium and in the temperature range 330-408 K. The low and the high pressur e limiting rate constants have been extracted from a complete falloff analy sis: k(0) = [He] x 1.0 x 10(-8) exp(-43.8 kJ mol(-1)/RT) cm(3) s(-1) and k( infinity) = 1.2 x 10(14) exp(- 63.7 kJ mol(-1)/RT) s(-1). We estimate an un certainty for these rate constants of +/-30%. Both rate constants have been discussed in terms of statistical unimolecular rate theory. Very good agre ement between the calculated and the experimental rate constants has been f ound.