A dc discharge in a dilute flow of PF3 in He was used as a source of PF(b(1) Sigma(+)) molecules in a flow reactor to measure the radiative lifetime and quenching rate constants for 38 reagent molecules at 300 K. The concentration of PF(b(1) Sigma(+)) in the reactor was about 2 x 10(8) molecule cm(-3). The decay rate of the PF(b(1) Sigma(+)) concentration was monitored from the intensity of the PF(b-->X) transition, and the radiative lifetime was measured to be 9.7 +/- 1.2 ms. The quenching rate constants are small, except for O-2 and Cl-2, and in the range 10(-12)-10(-14) cm(3) molecule(-1) s(-1). The dependence of the other rate constants on properties of the reagent is consistent with an electronic-to-vibrational (E-V) quenching mechanism, and this was confirmed by studying several isotopic pairs of molecules, such as H-2/D-2, H2O/D2O, and CH3CN/CD3CN. The quenching rate constants are compared to predictions of a model for E-V energy transfer. The reaction with O-2 proceeds by electronic energy transfer to give O-2(b(1) Sigma(+)).