Molecular Iodine Fluorescence Using a Green Helium−Neon Laser

Excitation of molecular iodine vapor with a green (543.4 nm) helium−neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature values. The use of a green helium−neon laser provides advantages in data collection, data analysis, cost, and safety relative to other I 2 excitation sources.