Hole-burning techniques

The chapter is divided into five sections. In Sec. Ill, we discuss how the molecular structure of crystal violet (CV), which is one of TPM dyes selected, is sensitive to its surrounding solvent molecules in solution. Recently, subtle structural differences in the ground state of CV was identified in alcohols by means of a femtosecond spectral hole-burning technique [19-21], Two key points of these studies are (1) proposal of a novel class of isomers, which are differentiated from one another by solvation and (2) conclusive decision of a long-run dispute over 50 years on whether the ground-state conformational isomers exist. 

Many studies concluded that only D3-symmetry is possible and denied C2-symmetry structures. However, the authors failed to explain the temperature and pressure dependence of the absorption spectrum as the substantial evidence for two ground states. On the other hand, only the temperature and the pressure dependence of the absorption spectrum evidenced the two ground states. Thus, no one has proposed any models of explaining comprehensively all the previous experimental observations and theoretical calculations. We found a convincing model of CV involving two ground states from experimental observations favored by tunable-excitation femtosecond spectral hole-burning technique and theoretical calculations. 

TLS have been probed effectively in ultrasonic experiments. An interesting strategy is used in these measurements. This is the so-called hole burning technique. When the intensity of the acoustic pulse is sufficiently high, the two states in TLS become equally populated and therefore the absorption from the acoustic field becomes saturated. As a result, the subsequent pulse suffers a reduced attenuation. Thus the high intensity sound pulse has burnt a hole in the occupation number at an energy, E =hco with a width Aa>. This is illustrated in Figure 9.06 for the... 

The transient spectral hole burning technique has been used to... 

There is another way of measuring of an optical transition which is not based on a coherent optical effect but also employs a coherence property of the laser, namely, its monochromaticity. In the hole-burning technique, as in the OFID method, a cw dye laser is used to create a hole in the absorption spectrum. When this hole is transient, its width, being determined in the low-intensity limit by 2( 7 ) , may be probed by side-band modulation as first demonstrated by Szabo on ruby. When the hole is permanent, as is the case in photochemical hole-burning, the width may be easily measured by means of a narrow-band excitation spectrum as first performed by de Vries and Wiersma on dimethyl j-tetrazine in durene. ... 

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 ... 

Masciangioli, T., Devanathan, S., Cusanovich, M.A., ToUin, G., and el-Sayed, M.A., Probing the primary event in the photocycle of photoactive yellow protein using photochemical hole-burning technique, Photochem. Photobiol, 72,5, 639-644,2000. 

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