Resonant non-linear spectroscopy in strong fields

A method is presented to describe multiple resonant non-linear spectra in the presence of strong laser fields. The Liouville equation for the density operator of the molecular system is transformed to a time-independent linear equation system. This can be easily solved rigorously by numerical methods or, after partitioning into a strong-field part and a perturbation, the solution can be obtained analytically by a novel perturbative approach. The results account for power broadening. Rabi splitting of signals, and power-induced extra resonances, the latter being related to the pure dephasing-induced resonances in the weak-field limit. The method can be applied to a large number of multiple resonant non-linear spectroscopies, especially CARS, CSRS, coherent Rayleigh scattering and sum- or difference-frequency generation.     

An enzymatic assay for monitoring serum,cerebrospinal fluid (CSF), and urine levels of recently developed antibiotics of theβ-lactam type

Analytical and Bioanalytical Chemistry -     

Capacitive-discharge-heated anisotropic pyrolytic graphite furnace used for atomic absorption spectrometry Part. 1 Thoeretical Modelling of the Heating Characteristics of the Furnace Surface and of the Gas Phase

A model of the temperature distribution in the tube wall and in the gas phase of an anisotropic pyrolytic graphite furnace heated by capacitive discharge technique is proposed. The heat loss from the graphite tube by conduction via the contact electrodes to the water-cooled electrode supports and by radiation to its surroundings are the main processes condidered. In calculating the gas temperature, heat transfer by conduction from the tube wall to the gas phase is the only mode taken into account. The instantaneous temperature of a graphite furnace is expressed in the form of a differential equation. A finite-difference form of the differential equation is used in a computer program to calculate the temperature at each time step. The computer simulation offers the capability of studying the factors affecting the characteristics of temperature/time profiles and the distribution of surface and gas phase temperatures of the furnace. The results of simulation studies of the effect of the capacitance and the initial voltage of the capacitor bank on the heating characteristics of the furnaces show a reasonable agreement with those obtained experimentally.     

Conformal gauge fixing in Minkowski space

Conformal gauge fixing on simply connected parts of world sheets in Minkowski space is examined in detail. It is proved that conformal gauge fixing can be imposed, including the usual boundary conditions.     

Decay of correlations. IV. Necessary and sufficient conditions for a rapid decay of correlations

We considerN-particle systems whose probability distributions obey the master equation. For these systems, we derive the necessary and sufficient conditions under which the reducedn-particle (n) probabilities also obey master equations and under which the Ursell functions decay to their equilibrium values faster than the probability distributions. These conditions impose restrictions on the form of the transition rate matrix and thus on the form of its eigenfunctions. We first consider systems in which the eigenfunctions of theN-particle transition rate matrix are completely factorized and demonstrate that for such systems, the reduced probabilities obey master equations and the Ursell functions decay rapidly if certain additional conditions are imposed. As an example of such a system, we discuss a random walk ofN pairwise interacting walkers. We then demonstrate that for systems whoseN-particle transition matrix can be written as a sum of one-particle, two-particle, etc. contributions, and for which the reduced probabilities obey master equations, the reduced master equations become, in the thermodynamic limit, those for independent particles, which have been discussed by us previously. As an example of suchN-particle systems, we discuss the relaxation of a gas of interacting harmonic oscillators.Supported in part (grants to D.B. and K.E.S.) by the Advanced Research Projects Agency of the Department of Defense as monitored by the U.S. Office of Naval Research under Contract N00014-69-A-0200-6018, and in part (grant to I.O.) by the National Science Foundation.