Rydberg state absorption spectroscopy of Br(CH2)nI (n=1–3)

The absorption spectra of jet-cooled bromoiodomethane (CH2BrI), 1,2-bromoiodoethane (Br(CH2)2I) and 1,3-bromoiodopropane (Br(CH2)3I) were measured in the spectral range 1600–2100 Å, and were compared with the corresponding monohalide absorption spectra. A pronounced broadening of the halogen nonbonding→Rydberg transition was observed in CH2BrI and in Br(CH2)2I whereas the transition width was considerably smaller in Br(CH2)3I. These results are rationalized in terms of a mixing of the halogen Rydberg states and the C–X (X=Br,I) antibonding state. The photochemical implications of these spectra are discussed in connection with a possible Rydberg state selective photochemistry.