Raman probes

Another application to biomedicine is to use Raman probing to study DNA biotargets and to identify sequence genes. In fact SERS has been applied to such problems [174]. 

Major breakthroughs in early ultrafast VER measurements were made in 1972 by Laubereau et al [22], who used picosecond lasers in an SRS pump-incoherent anti-Stokes Raman probe configuration, to study VER of C-H... 

Another important breaktlirough occurred with the 1974 development by Laubereau et al [24] of tunable ultrafast IR pulse generation. IR excitation is more selective and reliable than SRS, and IR can be used in pump-probe experiments or combined with anti-Stokes Raman probing (IR-Raman method) [16] Ultrashort IR pulses have been used to study simple liquids and solids, complex liquids, glasses, polymers and even biological systems. 

Por IR-Raman experiments, a mid-IR pump pulse from an OPA and a visible Raman probe pulse are used. The Raman probe is generated either by frequency doubling a solid-state laser which pumps the OPA [16], or by a two-colour OPA [39]. Transient anti-Stokes emission is detected with a monocliromator and photomultiplier [39], or a spectrograph and optical multichannel analyser [40]. 

Similar to IR sensors, process analysis is the prevalent application area. Due to the applicability of standard VIS instrumentation, Raman probes have been used for more than two decades65, 66. Typically, Raman probes are applied where near-IR probes fail and hence are in direct competition to mid-IR probes. 

It is more difficult to perform ultrafast spectroscopy on neat H20 (than it is on H0D/D20 or HOD/H20) since the neat fluid is so absorptive in the OH stretch region. One innovative and very informative technique, developed by Dlott, involves IR pumping and Raman probing. This technique has a number of advantages over traditional IR pump-probe experiments The scattered light is Stokes-shifted, which is less attenuated by the sample, and one can simultaneously monitor the populations of all Raman-active vibrations of the system at the same time. These experimental have been brought to bear on the spectral diffusion problem in neat water [18, 19, 75 77],... 

A final experiment was completed with a very slow dose of the reducing agent in an attempt to monitor the formation of intermediate and product using the in-situ Raman probe. A... 

Figure 7.3 Optical path of a commercial Raman probe. Adapted, with permission, Copyright 2004 Kaiser Optical Systems, Inc.

Figure 7.4 Collection of commercial Raman probes designed for different installations (a) laboratory scale probe with interchangeable immersion or noncontact optics, shown with immersion option (b) probe shown in (a) installed in laboratory fermentation reactor (c) production scale immersion probe (d) probe shown in (c) installed in a glass reactor (e) gas phase probe with flow through cell (f) probe shown in (e) installed in process piping (g) wide area illumination (WAI) noncontact probe after completion of a pharmaceutical tablet coating operation. Adapted, with permission. Copyright 2004 Kaiser Optical Systems, Inc.

G.M. Hamminga, G. Mul and J.A. Moulijn, Applicability of fiber-optic-based Raman probes for on-line reaction monitoring of high-pressure catalytic hydrogenation reactions, Appl. Spectrosc., 61, 470 78 (2007). 

Fiber-Optic Raman Probes for Biomedical and Pharmaceutical Applications... 

Abstract This chapter reviews the development of optical fiber probe Raman systems and their applications in life science and pharmaceutical studies. Especially, it is focused on miniaturized Raman probes which open new era in the spectroscopy of the life forms. The chapter also introduces the important optical properties of conventional optical fibers to use for Raman probes, as well as new types of optical fiber and devices, such as hollow optical fibers and photonic crystai fibers. 

By inserting the Raman probe into the channel of various endoscopes, we can access the inside of the stomach, the large and small intestines, the bronchus, and portions of the pancreatic and bile ducts. If it is used with a laparoscope, the accessible areas expand to the liver and the outer walls of the digestive organs. If the probe is narrow enough to insert in hypodermic... 

Fig. 2.1. Schematic representations of the confocal type Raman probe (A) and the miniaturized Raman probe (B)...

Fig. 2.5. Head structures of the miniaturized fiber-optic Raman probes developed by Motz et al. (modified from [29])...

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