Spectral hole burning optical absorption

One goal of the research in the Moerner group at IBM was the exploration of ultimate limits to the spectral hole-burning optical storage process. A particularly interesting limit on the SNR of a spectral hole results from the finite number of molecules that contribute to the absorption profile near the hole. Due to unavoidable number of fluctuations in the density of molecules in any spectral interval, there should exist a spectral noise on an inhomogeneous... 

Our first steps toward the single-molecule regime arose from work at IBM Research in the early 1980s on persistent spectral hole-burning effects in the optical transitions of impurities in solids (for a review, see [20]). Briefly, if a molecule with a strong zero-phonon transition and minimal Franck-Condon distortion is doped into a solid and cooled to liquid helium temperatures, the optical absorption becomes inhomogeneously broadened (Fig. 2.2A). The width of the lowest electronic transition for any one molecule (homogeneous width, Yjj) becomes very small because few phonons are present, while at the... 

For spectral hole-burning, the ionization step is preceded by a pulse from a tunable IR laser. This pulse resonantly alters a specific population in the beam, which is probed as a decrease in the ion signal [13-18]. This technique produces ground-state IR absorption spectra of optically selected as well as mass-selected molecules. The OH and NH stretching frequencies are especially highly specific for difierent tautomeric forms as well as for hydrogen-bonded structures. 

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