The reaction of metastable Ar(P-3(0,2)) atoms with PCl3 has been developed as a source of metastable PCl(b(1) Sigma(+)) molecules in a flow reactor at 300 K. The total quenching rate constants were measured for 23 molecules, and they are in the 2 x 10(-14) to 3 x 10(-11) cm(3) molecule(-1) s(-1) range. An electronic-to-vibrational (E-V) energy-transfer mechanism is used to discuss the quenching of PCl(b(1) Sigma(+)), and the experimental rate constants are compared to similar data for PF(b(1) Sigma(+)), NCl(b(1) Sigma(+)), and NCl(b(1) Sigma(+)) molecules. An influence of the type of halogen substituent in the reagent molecule on the quenching rate constants is identified, and a role for attractive molecular interactions needs to be added to the E-V model. The Ar(P-3(0.2)) + PCl3 reaction gives vibrationally excited PCl(b(1) Sigma(+)) molecules and the Delta nu=+1 and +2 sequences were observed in addition to the Delta nu=0 main sequence.