Steric effects in chemiluminescent reactions of metastable Ca*, Sr* atoms with isomeric propyl halides

Reactions of metastable alkaline earth atoms with normal and branched propy l halides were studied in a beam-gas arrangement. Chemiluminescence spectra of alkaline earth monohalides were observed for calcium and strontium reac tions. Some differences in the CaX (B(2)Sigma(+)/A(2)Pi) branching ratio we re found with isomeric variation of the targets. Total collision cross-sect ions for Mg* and Ca* reactions are independent of the isomeric substitution ; for strontium the values for isopropyl iodide are 50% higher than those f or normal propyl iodide target. Differences in chemiluminescence cross-sect ions are found for reactions of calcium with propyl iodides and propyl chlo rides. (C) 1999 Elsevier Science B.V. All rights reserved.