Broadband spectroscopy

There are numerous applications of white light generation and filamentation that span across disciplines, such as time-resolved broadband spectroscopy, generation of few cycle pulses [37], LIDAR [31], material modification [2], and... 

M. W. Evans, G. J. Evans, W. T. Coffey, and P. Grigolini, Molecular Dynamics and Theory of Broadband Spectroscopy, Wiley-Interscience, New York, 1982. 

The studies described in Sects. 4.1 and 4.2 were performed with monochromatic laser sources. To provide the information content of broadband spectroscopy, Bradshaw et al. [3] extended the prism coupling approach of broad angular width... 

In recent years, several technologies such as white noise stimulation, hydrodynamic focusing and trapping arrays have been implemented within single cell impedance microfluidic cytometry to achieve broadband spectroscopy, improvement in sensitivity and continuous time course measurements. 

Nowadays, the combination of laser ablation with Fourier transform microwave spectroscopy techniques, in supersonic jets, has enabled the gas-phase study of such systems. In this chapter, these techniques, including broadband spectroscopy, as well as results of their application into the study of the conformational panorama and structure of biomolecular building blocks, such as amino acids, nucleic bases, and monosaccharides, are briefly discussed, and with them, the tools for conformational assignation - rotational constants, nuclear quadrupole coupling interaction, and dipole moment. 

M. Islam, L. Ciaffoni, G. Hancock, G.A.D. Ritchie, Demonstration of a novel laser-driven light source for broadband spectroscopy between 170 nm and 2.1 xm. Analyst 138, 4741-4745... 

Figure 2 (a) A typical variation of e and e" over the frequency range of 10 -10 Hz that is nominally probed by broadband spectroscopy, (b) The different types of dielectric instruments mapped to the frequency ranges they probe. Reproduced with permission from Kremer, F. Schonhals, A. Broadband Dielectric Spectroscopy Springer Berlin, Germany, 2003, p. 36. ... 

Unlike the typical laser source, the zero-point blackbody field is spectrally white , providing all colours, CO2, that seek out all co - CO2 = coj resonances available in a given sample. Thus all possible Raman lines can be seen with a single incident source at tOp Such multiplex capability is now found in the Class II spectroscopies where broadband excitation is obtained either by using modeless lasers, or a femtosecond pulse, which on first principles must be spectrally broad [32]. Another distinction between a coherent laser source and the blackbody radiation is that the zero-point field is spatially isotropic. By perfonuing the simple wavevector algebra for SR, we find that the scattered radiation is isotropic as well. This concept of spatial incoherence will be used to explain a certain stimulated Raman scattering event in a subsequent section. 

Toleutaev B N, Tahara T and Hamaguchi H 1994 Broadband (1000 cm multiplex CARS spectroscopy application to polarization sensitive and time-resolved measurements Appl. Phys. 59 369-75... 

Aue W P, Kharan J and Ernst R R 1976 Homonuclear broadband decoupling and two-dimensional J-resolved NMR spectroscopy J. Chem. Phys. 64 4226-7... 

Decoupling (Section 13 17) In NMR spectroscopy any process that destroys the coupling of nuclear spins between two nuclei Two types of decoupling are employed in NMR spectroscopy Broadband decoupling removes all the H- C couplings ojf resonance decoupling removes all H- C couplings except those between directly bonded atoms... 

In C NMR spectroscopy, three kinds of heteronuclear spin decoupling are used In proton broadband decoupling of C NMR spectra, decoupling is carried out unselectively across a frequency range which encompasses the whole range of the proton shifts. The speetrum then displays up to n singlet signals for the n non-equivalent C atoms of the moleeule. 

Kremer F. and Schonhals, A., Eds., Broadband Dielectric Spectroscopy, Springer, Berlin, 2003. 

Figure 12.1 Schematic of the spectroelectrochemistry apparatus at the University of Dlinois. The thin-layer spectroelectrochemical cell (TLE cell) has a 25 p.m thick spacer between the electrode and window to control the electrolyte layer thickness and allow for reproducible refilbng of the gap. The broadband infrared (BBIR) and narrowband visible (NBVIS) pulses used for BB-SFG spectroscopy are generated by a femtosecond laser (see Fig. 12.3). Voltammetric and spectrometric data are acquired simultaneously.

Lagutchev A, Hambir SA, Dlott DD. 2007. Nonresonant background suppression in broadband vibrational sum-frequency generation spectroscopy. J Phys Chem C 111 ... 

Experimental limitations initially limited the types of molecular systems that could be studied by TRIR spectroscopy. The main obstacles were the lack of readily tunable intense IR sources and sensitive fast IR detectors. Early TRIR work focused on gas phase studies because long pathlengths and/or multipass cells could be used without interference from solvent IR bands. Pimentel and co-workers first developed a rapid scan dispersive IR spectrometer (using a carbon arc broadband IR source) with time and spectral resolution on the order of 10 ps and 1 cm , respectively, and reported the gas phase IR spectra of a number of fundamental organic intermediates (e.g., CH3, CD3, and Cp2). Subsequent gas phase approaches with improved time and spectral resolution took advantage of pulsed IR sources. 

MHz (55Mn). For 1H MRI experiments, a 25-mm birdcage rf insert was used. For other nuclei, the broadband rf probe supplied with the instrument for high resolution NMR spectroscopy with a saddle-shaped rf coil (6-mm inside diameter) was used with the external aluminum shield removed. 

Figure 2. Rates of photodegradation of the copolymer when exposed to a broadband UV source (shortest wavelength 297 nm) (A) change in absorbance as a function of irradiation time in the wavelength range of 250-450 nm (spectrum measured on films) (B) change in absorbance at 3580 cm 1 measured by FTIR spectroscopy (rate of hydroxyl formation)...

We note that optimal control is a universal tool for experiment design and has also, in solid-state NMR spectroscopy, found additional applications in the design of homonu-clear dipolar recoupling [41], broadband rf pulses and quantum gates [71], building blocks of symmetry-based recoupling experiments [129], quadrupolar multiple-quantum MAS experiments [165], and improved pulses for quadrupolar nuclei [166]. Numerous references to further applications with regard to liquid-state NMR can be found in [72]. 

The broadband analysis was confirmed by the experimental results mentioned in Sect. 5.4.1. This method can also be further enhanced by some of the techniques described in Sects. 5.4.2 and 5.4.3. The conclusion is that these methods of microcavity-enhanced optical absorption sensing provide compact, inexpensive, and sensitive detectors for molecular species in the ambient gas or liquid, and that further increases in sensitivity can be implemented to make them even more competitive. The molecular-transition specificity that is implicit in absorption spectroscopy is a limiting restriction, but the surface-enhanced Raman sensing that is enabled by metallic nanoparticles on the microresonator surface can significantly increase the number of molecular species that could be detected. 

In conclusion, when a WGM is excited in a dielectric microresonator, its evanescent component provides a convenient probe of the microresonator s surroundings. Various ways to implement evanescent-wave sensing have been devised, but the emphasis of this chapter has been on microcavity-enhanced absorption spectroscopy. The techniques described here have broad applicability, can even be used with broadband sources, and lend themselves well to further enhancement methods. We are looking forward to continuing our development of these sensors. 

The emerging analytical technique of laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopy technique that has the potential for real-time man-portable chemical analysis in the field. Because LIBS is simultaneously sensitive to all elements, a single laser shot can be used to record the broadband emission spectra, which provides a chemical fingerprint of a material. 

---