Hyperfine-structure study in the P sequence of 23 Na using quantum-beam spectroscopy

Describes use of the quantum-beat method to study hyperfine structure in the 5 2 P 3/2 and 6 2 P 3/2 states of 23 Na. A pulsed dye laser, frequency-doubled into the UV region, was used to excite sodium atoms abruptly in a beam. The fluorescent light was recorded with a fast transient digitiser, interfaced to a micro-computer. Theoretical calculations using many-body perturbation theory were performed for the entire P sequence measured so far, taking polarisation and correlation effects into account separately. Very good agreement between experimental and theoretical values was obtained

High-contrast Doppler-free transmission spectroscopy

By applying Doppler-free saturated absorption spectroscopy in the regime of high integrated sample absorption, high-contrast Doppler-free laser transmission signals can be obtained as demonstrated in experiments on the sodium D lines. Natural linewidth background-free signals are observed

Three-photon-excited fluorescence detection of atomic hydrogen in an atmospheric-pressure flame

By using three-photon excitation at 291.7 nm of the n $=$ 4 hydrogen level and observing Balmer-$\beta$ radiation at 486.1 nm, hydrogen atoms in an atmospheric C2H2/O2 flame have been detected. Other schemes for hydrogen detection were also tried, and the results are discussed

Enhanced He-alpha emission from "smoked" Ti targets irradiated with 400nm, 45 fs laser pulses

We present a study of He-like 1s(2)-1s2p line emission from solid and low-density Ti targets under similar or equal to 45 fs laser pulse irradiation with a frequency doubled Ti: Sapphire laser. By varying the beam spot, the intensity on target was varied from 10(15) W/cm(2) to 10(19) W/cm(2). At best focus, low density "smoked" Ti targets yield similar to 20 times more He-alpha than the foil targets when irradiated at an angle of 45 degrees with s-polarized pulses. The duration of He-alpha emission from smoked targets, measured with a fast streak camera, was similar to that from Ti foils

Laser spectroscopy using beam-overlap modulation

A new Doppler-free laser spectroscopy method is demonstrated that employs modulation of the position of a laser beam rather than the commonly used intensity or polarization modulation. The technique is applicable in saturated absorption as well as fluorescence measurements, as is illustrated in experiments on sodium and iodine lines. A particular feature of the method is that Doppler- and background-free fluorescence spectra can be recorded without using intermodulation techniques

Defect configurations and dynamical behavior in a Gay-Berne nematic emulsion

To model a nematic emulsion consisting of a surfactant-coated water droplet dispersed in a nematic host, we performed a molecular dynamics simulation of a droplet immersed in a system of 2048 Gay-Berne ellipsoids in a nematic phase. Strong radial anchoring at the surface of the droplet induced a Saturn ring defect configuration, consistent with theoretical predictions for very small droplets. A surface ring configuration was observed for lower radial anchoring strengths, and a pair of point defects was found near the poles of the droplet for tangential anchoring. We also simulated the falling ball experiment and measured the drag force anisotropy, in the presence of strong radial anchoring as well as zero anchoring strength.Comment: 17 pages, 15 figure

Theory and applications of atomic and ionic polarizabilities

Atomic polarization phenomena impinge upon a number of areas and processes in physics. The dielectric constant and refractive index of any gas are examples of macroscopic properties that are largely determined by the dipole polarizability. When it comes to microscopic phenomena, the existence of alkaline-earth anions and the recently discovered ability of positrons to bind to many atoms are predominantly due to the polarization interaction. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. Accurate polarizabilities for the group I and II atoms and ions of the periodic table have recently become available by a variety of techniques. These include refined many-body perturbation theory and coupled-cluster calculations sometimes combined with precise experimental data for selected transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index measurements in microwave cavities, ab initio calculations of atomic structures using explicitly correlated wave functions, interferometry with atom beams, and velocity changes of laser cooled atoms induced by an electric field. This review examines existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on cold-atom physics and the metrology of atomic frequency standards.Comment: Review paper, 44 page

Sub-Doppler spectroscopy of Rb atoms in a sub-micron vapor cell in the presence of a magnetic field

We report the first use of an extremely thin vapor cell (thickness ~ 400 nm) to study the magnetic-field dependence of laser-induced-fluorescence excitation spectra of alkali atoms. This thin cell allows for sub-Doppler resolution without the complexity of atomic beam or laser cooling techniques. This technique is used to study the laser-induced-fluorescence excitation spectra of Rb in a 50 G magnetic field. At this field strength the electronic angular momentum J and nuclear angular momentum I are only partially decoupled. As a result of the mixing of wavefunctions of different hyperfine states, we observe a nonlinear Zeeman effect for each sublevel, a substantial modification of the transition probabilities between different magnetic sublevels, and the appearance of transitions that are strictly forbidden in the absence of the magnetic field. For the case of right- and left- handed circularly polarized laser excitation, the fluorescence spectra differs qualitatively. Well pronounced magnetic field induced circular dichroism is observed. These observations are explained with a standard approach that describes the partial decoupling of I and J states