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

Reactions of metastable alkaline earth atoms with normal and branched propyl halides were studied in a beam-gas arrangement. Chemiluminescence spectra of alkaline earth monohalides were observed for calcium and strontium reactions. Some differences in the CaX (B 2Σ+ / A 2Π) branching ratio were found with isomeric variation of the targets. Total collision cross-sections for Mg∗ and Ca∗ reactions are independent of the isomeric substitution; for strontium the values for isopropyl iodide are 50% higher than those for normal propyl iodide target. Differences in chemiluminescence cross-sections are found for reactions of calcium with propyl iodides and propyl chlorides.