Spectroscopy of vibrational transitions

Hamm P, Lim M, DeGrado WF, Hochstrasser RM. Two dimensional self-heterodyned spectroscopy of vibrational transitions of a small globular peptide. J Chem Phys 2000 112 1907-1916. 

Spectroscopy of rovibrational transitions in the electronic ground state can take advantage of these special conditions. The low translational temperature of the molecules increases the absorption rate significantly, and efficient excitation is possible even on weak overtone transitions [89]. This allows one to use simpler laser sources, which also simplifies experimentation. Due to the relatively long lifetime of vibrational levels of molecules ( msec to days), the potential line resolution can be huge. Spectroscopy of vibrational transitions on cold and localized samples of molecular ions was first achieved using HD+ ions [90]. 

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