Overlapping resonances interference-induced transparency: The S _0 → S _2S _1 photoexcitation spectrum of pyrazine

摘要

The phenomenon of overlapping resonances interference-induced transparency (ORIT) is introduced and studied in detail for the S _0 → S _2S _1 photoexcitation of cold pyrazine (C _4H _4N _2). In ORIT, a molecule becomes transparent at specific wavelengths due to interferences between envelopes of spectral lines displaying overlapping resonances. An example is the S _2 S _1 internal conversion in pyrazine where destructive interference between overlapping resonances causes the S _0 → S _2S _1 light absorption to disappear at certain wavelengths. ORIT may be of practical importance in multi-component mixtures where it would allow for the selective excitation of some molecules in preference to others. Interference-induced cross section enhancement is also shown.