Hole-burning techniques spectroscopy

In addition to the relation of hole burning techniques to dynamic saturation methods, it is also important to stress the close relation to another rather different technique, namely, Mossbauer spectroscopy. The hole burning technique has been called the optical analog of the Mossbauer effect. The relation is very close, indeed. On the one hand, both techniques work at the ultimate limit of resolution given by the natural line width. It is not the lasers which limit the resolution in hole burning it is the fast excited state lifetimes which set the resolution limit. For organic dye molecules these lifetimes are in the nanosecond time regime. Conse-... 

For nucleotides, the charge on the phosphate group generally precludes the use of the 1R-R2PI hole burning technique. Instead, it is possible to study ions in a trap by IR multiphoton dissociation (IRMPD). The characteristics of a free electron laser, such as FELIX, with its macro and micro pulses, are very suitable for this type of multiphoton IR spectroscopy [58]. Since there is no isomer selection in this case, the interplay with theory is especially important and the occurrence of multiple structural forms could complicate interpretation, van Zundert et al. compared results for neutral (by DRS) and protonated (by IRMPD) adenine and 9-methyladenine in the same mid-IR frequency range of 525-1,750 cm ... 

Pairwise EET rates cannot be directly measured in antenna systems. The closest approach to direct determination is offered on the one hand by time resolved picosecond and sub-picosecond absorption and fluorescence measurements and on the other hand by hole burning spectroscopies. Time resolved techniques do not detect transfer between isoenergetic sites. A somewhat more indirect approach to determining pairwise rates is that of analysing excited state lifetime data in terms of a particular antenna and an EET model. 

We are beginning to develop a detailed understanding of these methods (18,21,30,33,34,37-40,42,44,47-49), many of which are described in this book. We have recently demonstrated a series of novel nonlinear all-IR spectroscopic techniques (IR-pump-IR-probe, IR-three-pulse photon echoes, IR-dynamic hole burning, IR-2D spectroscopy), all of them utilizing intense femtosecond IR pulses, with the intention to develop new multidimensional spectroscopic tools to study the structure and the dynamics of proteins (30,31,41,42,50-53). We shall summarize in this contribution our work, its underlying principles, and its applications. 

Hole burning The photohleaching of a feature, normally a narrow range, within an inhomogeneous broader absorption or emission band. The holes are produced by the disappearance of resonantly excited molecules as a result of photophysical or photochemical processes. The resulting spectroscopic technique is site-selection spectroscopy. 

The very first fluorescence spectra of jet-cooled exciplexes indicated the existence of two types of ground-state van der Waals adducts. For instance, the anthracene-dimethylaniline system displayed two types of cluster bands in the fluorescence excitation spectrum broad ( 150 cm ) and structureless, leading to typical ex-ciplex emission, and narrow (1 cm ), leading to resonance-type emission [10, 20]. It was assumed that they are due to different 1 1 adducts, distinguished by different geometries. Recently, laser-based techniques were developed that allow the discrimination of different species. One is hole-burning spectroscopy and another— mass-selected photoionization. 

A comprehensive review of hole burning spectroscopy of species in glasses has been prepared by Haarer and Silbey. Electric field effects on the spectral holes for perylene in Shpol skii matrices in n-heptane provide a useful extension of this technique . The limitations of the thermal lens method for the measurement of fluorescence yields have been examined and discussed . It is pointed out that the... 

Within the last one and a half decades, it became possible to perform experiments directly on the atomic and molecular level. This came with the improvement of existing experimental techniques such as electron microscopy, where the resolution was increased to make single atoms visible [1] high-resolution spectroscopy of single ions or atoms trapped in a radio frequency field or in focused laser beams [2-4] and the spectroscopic isolation of single molecules in solids at cryogenic temperatures [5-7], which evolved from spectral hole-burning spectroscopy. 

A number of books and reviews which describe some of the new experimental techniques have appeared. Topics covered include hole burning spectroscopy,8 various forms of picosecond and femtosecond spectroscopy, femtosecond coherent spectroscopy, ultrafast time-... 

The true natural line width of the states without the complication of the phonon wing can be studied by low-temperature absorption holeburning experiments. Because Friedrich ([10] in this volume) presents a discussion of hole burning in protein spectroscopy, we confine ourselves to a brief review of the results of Vanderkooi using low-temperature fluroescence techniques. 

Finally, an important and useful variant in hole burning spectroscopy is the temperature cycling technique. A hole is burnt at low temperatures, then the temperature is varied in a cyclic fashion. The change in the hole width is measured as a function of Fb -, where T, is the bum tempera-... 

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