Continuum spectroscopy

Many other techniques have been used in addition to those discussed. For example, additional absorption techniqnes, generally beyond the scope of this article inclnde two-photon luminescence (287), thermal leasing (288), photoacoustic techniques (289), and white-light continuum spectroscopy (290). For further information, the reader is referred particnlarly to Reference 1. 

Adler-Golden, S.M. Franck-Condon analysis of thermal and vibrational excitation effects on the ozone Hartley continuum. J. Quant. Spectrosc. Radiat. Transf. 30, 175-185 (1983) Adler-Golden, S.M., Schweitzer, E.L., Steinfeld, J.I. Ultraviolet continuum spectroscopy of vibrationally excited ozone. J. Chem. Phys. 76, 2201-2209 (1982)... 

Figure B2.1.6 Femtosecond spectrometer for transient hole-burning spectroscopy with a continuum probe. Symbols used bs, 10% reflecting beamsplitter p, polarizer. The continuum generator consists of a focusing lens, a cell containing flowing water or ethylene glycol or, alternatively, a sapphire crystal and a recollimating lens.

Promotion of an electron in Hc2 from the (7 15 to a bonding orbital produces some bound states of the molecule of which several have been characterized in emission spectroscopy. For example, the configuration ((J l5 ) ((7 l5 ) ((7 25 ) gives rise to the 2i and bound states. Figure 7.24(a) shows the form of the potential curve for the state. The A-X transition is allowed and gives rise to an intense continuum in emission between 60 nm and 100 nm. This is used as a far-ultraviolet continuum source (see Section 3.4.5) as are the corresponding continua from other noble gas diatomic molecules. 

He2 ICl conformer using action spectroscopy to find the bound-free continuum associated with the He + He IC1(B, V = 3) dissociation limit. It would also be insightful to perform time-resolved experiments on the different conformers of these systems to directly monitor the kinetics for forming the different products and intermediates as a function of the different excited-state levels prepared. 

References 29-33 introduce the notion of coherence spectroscopy in the context of two-pathway excitation coherent control. Within the energy domain, two-pathway approach to coherent control [25, 34—36], a material system is simultaneously subjected to two laser fields of equal energy and controllable relative phase, to produce a degenerate continuum state in which the relative phase of the laser fields is imprinted. The probability of the continuum state to evolve into a given product, labeled S, is readily shown (vide infra) to vary sinusoidally with the relative phase of the two laser fields < ),... 

Breit-Wigner phase, two-pathway excitation, coherence spectroscopy energy domain, 180-182 low-lying resonance, continuum excitation, 169-170... 

Continuum excitation, coherence spectroscopy isolated resonance ... 

Correlation matrix, linear thermodynamics, regression theorem, 17-20 Coupled cluster (CC), ab initio calculations, P,T-odd interactions, 254-259 Coupled continuum, two-pathway excitation, coherence spectroscopy isolated resonances, 168-169 structureless excitation, 167 CPT theorem ... 

Two-dimensional constant matrix, transition state trajectory, white noise, 203-207 Two-pathway excitation, coherence spectroscopy atomic systems, 170-171 channel phases, 148-149 energy domain, 178-182 extended systems and dissipative environments, 177-185 future research issues, 185-186 isolated resonance, coupled continuum, 168-169... 

Jolly, W. L. Inorganic Applications of X-Ray Photoelectron Spectroscopy. 71, 149-182 (1977). Jorgensen, C. K. Continuum Effects Indicated by Hard and Soft Antibases (Lewis Acids) and Bases. 56, 1-66 (1975). 

No single development has influenced the field of EXAFS spectroscopy more than the development of synchrotron radiation sources, particularly those based on electron (or positron) storage rings. These provide a continuum of photon energies at intensities that can be from 103 to 106 higher than those obtained with X-ray tubes,... 

Now, we are not particular experts in X-ray and gamma-ray spectroscopy (nor mass spectroscopy, for that matter), but our understanding of those technologies is that they are used mainly in emission mode. Even when the exciting source is a continuum source, such as is found when an X-ray tube is used to produce the exciting X-rays for an X-ray Fluorescence (XRF) measurement, the measurement itself consists of counting the X-rays emitted from the sample after the sample absorbs an X-ray from the source. These measurements are themselves the equivalent of single-beam measurements and will thus also be Poisson-distributed in accordance with the basic physics of the phenomenon. 

Kieffer has estimated the heat capacity of a large number of minerals from readily available data [8], The model, which may be used for many kinds of materials, consists of three parts. There are three acoustic branches whose maximum cut-off frequencies are determined from speed of sound data or from elastic constants. The corresponding heat capacity contributions are calculated using a modified Debye model where dispersion is taken into account. High-frequency optic modes are determined from specific localized internal vibrations (Si-O, C-0 and O-H stretches in different groups of atoms) as observed by IR and Raman spectroscopy. The heat capacity contributions are here calculated using the Einstein model. The remaining modes are ascribed to an optic continuum, where the density of states is constant in an interval from vl to vp and where the frequency limits Vy and Vp are estimated from Raman and IR spectra. 

Abstract This chapter reviews the theoretical background for continuum models of solvation, recent advances in their implementation, and illustrative examples of their use. Continuum models are the most efficient way to include condensed-phase effects into quantum mechanical calculations, and this is typically accomplished by the using self-consistent reaction field (SCRF) approach for the electrostatic component. This approach does not automatically include the non-electrostatic component of solvation, and we review various approaches for including that aspect. The performance of various models is compared for a number of applications, with emphasis on heterocyclic tautomeric equilibria because they have been the subject of the widest variety of studies. For nonequilibrium applications, e.g., dynamics and spectroscopy, one must consider the various time scales of the solvation process and the dynamical process under consideration, and the final section of the review discusses these issues. 

Tomas et al. [281] have calculated the tautomeric equilibrium of 1,2,3-benzotriazole in the gas phase and compared their results to experimental data [282] derived from ultraviolet spectroscopy. Experiment suggests that 35 is about 4 kcal/mol more stable than 34 this result is consistent with calculations [281] at the MP2/6-31G level, which predict 35 to be 2.5 kcal/mol more stable than 34. The same level of theory predicts 33 to be 5.0 kcal/mol more stable than 32 in the parent triazole system. Although experimental data are available indicating 35 to be the dominant tautomer in CDCf and d6-dimethyl sulfoxide solutions [279, 283], this equilibrium does not appear to have been the subject of any modeling, continuum or otherwise. It may prove to be somewhat challenging, however. Tomas et al. point out that correlation effects favor 35 by about 5 kcal/mol at the MP2 level AMI, PM3, and HF calculations with moderate basis sets all predict... 

In chapter 1, Profs. Cramer and Truhlar provide an overview of the current status of continuum models of solvation. They examine available continuum models and computational techniques implementing such models for both electrostatic and non-electrostatic components of the free energy of solvation. They then consider a number of case studies with particular focus on the prediction of heterocyclic tautomeric equilibria. In the discussion of the latter they focus attention on the subtleties of actual chemical systems and some of the danger in applying continuum models uncritically. They hope the reader will emerge with a balanced appreciation of the power and limitations of these methods. In the last section they offer a brief overview of methods to extend continuum solvation modeling to account for dynamic effects in spectroscopy and kinetics. Their conclusion is that there has been tremendous progress in the development and practical implementation of useful continuum models in the last five years. These techniques are now poised to allow quantum chemistry to have the same revolutionary impact on condensed-phase chemistry as the last 25 years have witnessed for gas-phase chemistry. 

Near-edge X-ray absorption spectroscopy and bonding, 34 223-235 continuum spectral features, 34 234-235 edge widths, 34 233-234 energy shifts and coordination charge, 34 228... 

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