Electron-lattice kinetics of metals heated by ultrashort laser pulses

We propose a kinetic model of transient nonequilibrium phenomena in metals exposed to ultrashort laser pulses when heated electrons affect the lattice through direct electron-phonon interaction. This model describes the destruction of a metal under intense laser pumping. We derive the system of equations for the metal, which consists of hot electrons and a cold lattice. Hot electrons are described with the help of the Boltzmann equation and equation of thermoconductivity. We use the equations of motion for lattice displacements with the electron force included. The lattice deformation is estimated immediately after the laser pulse up to the time of electron temperature relaxation. An estimate shows that the ablation regime can be achieved.Comment: 7 pages; Revtex. to appear in JETP 88, #1 (1999

The XENON100 Dark Matter Experiment

The XENON100 dark matter experiment uses liquid xenon (LXe) in a time projection chamber (TPC) to search for Xe nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper we present a detailed description of the detector design and present performance results, as established during the commissioning phase and during the first science runs. The active target of XENON100 contains 62 kg of LXe, surrounded by an LXe veto of 99 kg, both instrumented with photomultiplier tubes (PMTs) operating inside the liquid or in Xe gas. The LXe target and veto are contained in a low-radioactivity stainless steel vessel, embedded in a passive radiation shield. The experiment is installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and has recently published results from a 100 live-days dark matter search. The ultimate design goal of XENON100 is to achieve a spin-independent WIMP-nucleon scattering cross section sensitivity of \sigma = 2x10^-45 cm^2 for a 100 GeV/c^2 WIMP.Comment: 23 pages, 27 figures; version accepted by journa

Probing ultrafast biological processes by picosecond spectroscopy.

A brief discussion of the initial events leading to the visual transduction process will be presented to illustrate the capabilities of picosecond spectroscopy

PICOSECOND ABSORPTION SPECTROSCOPY

Author Institution: Bell Laboratorie

Correlation of optical activity and nonlinear polarizability

This paper describes recent experiments in which optical sum frequency generation has been observed in liquids. The mechanism of coherent optical sum frequency generation in systems of randomly oriented molecules is closely related to that of optical activity, and the symmetry selection rules for the two processes are the same. The effect is observed experimentally in d- and l-optical isomers, for example, but vanishes in a racemic mixture. Details of the measurement of the nonlinear polarizability of optically active liquids are presented. The mechanism of sum frequency generation is explained in terms of the one-electron and the coupled-oscillator models of optical activity, and it is proposed that the ratio of the nonlinear polarizability to the optical rotatory power provides information in assessing the relative role of the two models

PICOSECOND DYNAMICS OF ELECTRONS IN FLUIDS

Author Institution: Bell LaboratoriesWe have investigated the picosecond kinetics of solvated electrons in various solvent solutions. The effect of excitation at 1060 nm and 1350 nm on the absorption spectrum of the solvated electron in dilute $Na/ND_{3}$ solution was monitored in the spectral range of 850-1500 nm. These experiments allow us to explain the cause of the band broadening. The relaxation time of the excited state of the solvated electron was determined to be $a\approx 2 \times 10^{-13}$ seconds. This ultra fast relaxation lifetime favors relaxation between bound states of the solvated electron center. Similar studies were conducted on the photoionization of $Na^{-}$ band in Na/dimethoxyethane, DME, solution. The absorption monitored in the range of 800 nm-1500 nm reveal two distinct absorption bands formed immediately after excitation with a 6 psec pulse at 530 nm. One is attributed to the ion-pair $Na^{+}e^{-}$ while the other, at longer wavelengths, is assigned to the solvated electron. The mechanism and kinetics of these processes will be discussed."