We consider an atom in interaction with a massless scalar quantum field. We discuss the structure of the rate of variation of the atomic energy for an arbitrary stationary motion of the atom through the quantum vacuum. Our main intention is to identify and to analyze quantitatively the distinct contributions of vacuum fluctuations and radiation reaction to the spontaneous excitation of a unifor...

Finding representative reaction pathways is important for understanding the mechanism of molecular processes. We propose a new approach for constructing reaction paths based on mean first-passage times. This approach incorporates information about all possible reaction events as well as the effect of temperature. As an application of this method, we study representative pathways of excitation m...

Bathorhodopsin-rhodopsin difference spectra of native 11-cis-rhodopsin and regenerated 9-cis-rhodopsin were measured at room temperature with a double-beam laser spectrophotometer after excitation at 532 nm. A detailed analysis of data obtained at 85 psec after excitation suggests that the bathorhodopsins generated from 11-cis- and 9-cis-rhodopsin differ in their extinction coefficients and tha...

Electron energy spectra for Hautodetaching states resulting from collisions of H' with He at 1 keV are rigorously calculated by including couplings between doubly excited states and continuum states and their interference with direct detachment processes. An energy sampling procedure, based on the Gauss quadratures, is used to discretize continuum states. The present theoretical result, for the...

Two-photon microscopy offers unique advantages for excitation of channelrhodopsin-2 (ChR2)-expressing neurons, but previous attempts had limitations in terms of the axial and temporal resolution. Emiliani and colleagues now use a scanless approach that combines generalized phase contrast and temporal focusing to shape two-photon excitation patterns and trigger single action potentials or trains...

Stochastic processes in the form of the classical Brownian motion or internal phonon fluctuations may be studied by the use of a microcantilever. We present certain dynamic aspects of the behavior of the noise and the delayed fluctuations exhibited by a microcantilever. In particular, we present an analytic solution describing the transient response of the oscillator and discuss how self-excita...

ATI can be followed by an inelastic collision of the ionized electron with the parent atomic particle resulting in an excitation of the ion. It may be a continuum state excitation producing the doubly charged ion or a discrete state which also enhances the doubly charged ion production. Absorption of a few quanta above the atomic threshold is sufficient to make this mechanism work. As a result ...

Accurately measuring the bulk minority carrier lifetime is one of the greatest challenges in evaluating photoactive materials used in photovoltaic cells. One-photon time-resolved photoluminescence decay measurements are commonly used to measure lifetimes of direct bandgap materials. However, because the incident photons have energies higher than the bandgap of the semiconductor, most carriers a...

Through laboratory experiments we examine internal wave generation above and in the lee of finite-amplitude periodic topography having various degrees of roughness. We show that internal waves are generated not only by flow over the hills but also by flow over “boundary-trapped” lee waves and by vigorous turbulence created in the lee of sharp-crested hills. For low values of the excitation freq...

An imaging spectrograph equipped with a CCD detector was employed to measure two-dimensional emission images from a glow discharge plasma in atomic emission spectrometry. The emission images at Zn I 334.50 nm for a zinc sample and at Cu I 324.75 nm for a copper sample could be obtained. Their emission intensities were not uniform in the radial direction of the plasma region but became weaker at...