We report the discovery of 25 previously unknown energy levels of even parity and 3 previously unknown energy levels of odd parity of the tantalum atom, including the last two unknown levels with energy values below 32500 cm-1. Thus, below 32500 cm-1, all levels predicted by theory have now been observed. These results are based on investigations of the hyperfine structure of 126 new spectral lines of the tantalum atom (Ta I) by means of laser spectroscopy. The observation of laser-induced fluorescence further led to the classification of 159 spectral lines. Additionally, 235 lines, observed in high resolution Fourier transform spectra, were classified by their wave numbers and their characteristic hyperfine patterns.

The hyperfine structures of 57 new spectral lines of the tantalum atom were investigated by means of laser excitation. From the hyperfine patterns we have determined the angular momenta J, the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 15 new energy levels of even parity and three new levels of odd parity. The observation of laser-induced fluorescence led to the classification of further 156 spectral lines for the first time. Additionally 92 lines, observed in high resolution Fourier transform spectra, were classified using a combination of their wavenumbers and their characteristic hyperfine patterns.

We have classified about 400 new spectral lines of neutral tantalum via laser excitation or observation of laser-induced fluorescence. 37 energy levels with even parity and seven levels with odd parity were found by means of systematic hyperfine structure investigations. For the new levels angular momentum, parity, magnetic hyperfine interaction constant A and electric quadrupole interaction constant B were deduced. In addition, we have classified 230 new lines observed in high resolution Fourier transform spectra by analysing their observed hyperfine structure patterns.

Relative intensity measurements of Al I and Al II spectral lines in the visible and ultraviolet spectral ranges are performed using a capacitively coupled high frequency double hollow electrode discharge. Branching ratios and intensity ratios within multiplets are determined. By using selected lifetimes absolute transition probabilites are calculated.

Wire-shaped gold specimens are placed in a new, improved high-pressure vessel, which is part of a fast capacitor-discharge circuit and in which static pressures above 600 MPa can be reached with distilled water as the pressure-transmitting medium. The specimens are self-heated resistively by a current pulse. The current through the specimen, the voltage drop across it, and its temperature are recorded as a function of time with submicrosecond resolution. The radial expansion of the specimen is determined with a CCD camera, Experiments are performed at different pressures. When the critical pressure is exceeded, there is no liquid–gas phase transition; hence, no sudden change in the thermal expansion rate is observed. The results for temperature, pressure, and specific volume at the critical point of gold are as follows: T c =7400±1100 K, p c =530±20 MPa, and v c =0.13±0.03 × 10 −3 m 3 ·kg −1 .

In earlier experiments we have studied pure elements with a fast pulse heating technique to obtain thermophysical properties of the liquid state. We report here results for thermophysical properties such as specific heat and dependences among enthalpy, electrical resistivity, and temperature, for four W–Re alloys (3.95, 21.03, 23.84, and 30.82 at % of Re) in a wide temperature range covering solid and liquid states. Thermal conductivity is calculated using the Wiedemann–Franz law for the liquid alloy, as.well as data for thermal diffusivity for the beginning of the liquid phase. Additionally, data for the entire temperature range studied have been analyzed in comparison with those of the constituent elements, tungsten and rhenium, since both metals have been studied previously with the same experimental technique. Such information is of interest in the field of metallurgy since W–Re alloys of low Re content in the region of mutual component solubility in the solid state are widely used as thermocouple materials for the purposes of high-temperature thermometry.

Wire shaped invar specimens are resistively volume heated as part of a fast capacitor discharge circuit, The following properties were measured simultaneously and time resolved with sub-mu s resolution: currents through the specimen by a pearson probe, voltage across the specimen by a voltage divider, temperature radiation of the specimen by an optical pyrometer and thermal expansion by a fast acting CCD-camera, These measurements allow the determination of heat capacity enthalpy, electrical resistivity, and density as function of temperature of the alloy In the solid and liquid state in the vicinity of the melting region, Thermal conductivity of invar is estimated from electrical resistivity using Wiedeman-Franz-law.Results of invar are compared with those of earlier obtained results of pure iron and nickel.

The particle density of ground-state chromium atoms within one cross section of an arc plasma was measured spatially resolved, and the spatial distribution of the line shape of the chromium resonance line at 427.48 nm was partly determined. The measurements were performed with a newly developed setup that combines the methods of resonance interferometry and refractive tomography. The wavelength of a dye laser was scanned over the investigated transition, and the refractive index was measured spatially and spectrally resolved by use of tomography. For each spatial point the particle density and the local line shape were calculated from the measured spectral refractivity distribution by the method of resonance interferometry. We describe the physical principles, the optical arrangement, and the numerical apparatus, and we discuss the results and further possibilities.

Performing laser-atomic beam spectroscopy, we have remeasured the transition frequencies and the fine structure splitting of the lithium, sodium and potassium resonance lines. Additionally, the isotope shifts6Li-7Li could be determined with high accuracy. Transition frequencies were determined by means of a high-precision lambdameter working at vacuum conditions, calibrated by saturation absorption of127I2. Frequency differences up to 1 THz could be determined with the help of a carefully calibrated marker etalon with systematical errors smaller than 1 MHz.

We report the observation of a band system between 510 and 540 nm in laser induced fluorescence spectra of Cs2 excited by Ar+ laser lines λexc = 488 nm, λexc 496.5 nm and λexc = 501.7 nm. Using potential energy curves of Cs2 and performing quantum mechanical simulations of the spectra we assign these new structures to the transition 3 1Σu+ → 1 1Σg+.

A new experimental technique suitable for real-time measurements has been developed which permits the determination of the spatial distribution of the electron density of a plasma with a time resolution commensurate with the 6 ns duration of a single laser pulse. The accuracy and sensitivity of the electron density measurements allow the application to low-temperature plasma diagnostics. The possibilities of the method were demonstrated by studying a steady state mini-arc argon plasma at atmospheric pressure. The measured electron densities with 2 cm plasma length spanned the range from to on the plasma axis.

Laserspectroscopic investigations were performed on a collimated atomic beam of barium (natural isotope abundance). The metastable ground levels (3D1,2,3 and 1D2) of the investigated lines were populated by a discharge burning in barium vapour directly in front of the oven hole. We could investigate 14 spectral lines between 580 and 690 nm. The tensor polarizabilities of the upper and the lower level as well as the differences in the scalar polarizabilities could be determined. Spectra in magnetic fields up to 0.03 Tesla showed no deviation from the pattern resulting from a simple Russell-Sounders coupling.

Wire-shaped zinc samples were resistively volume heated as part of a fast-capacitor discharge circuit. Time-resolved measurements with submicrosecond resolution of the current through the specimen, the voltage drop across it, and the thermal expansion of the specimen as a Function of time allow determination of the enthalpy, electrical resistivity, and density at different temperatures up to superheated liquid states of zinc far above the normal boiling point. High static pressures, up to 3800 bar of the ambient medium water, were used. An estimate of the critical pressure for zinc is given by investigations of the stability of the sample with a framing CCD camera, taking pictures of different samples varying the ambient static pressure. The critical volume and the critical temperature are obtained by means of an extrapolation of measured data at different pressures.

A new setup for plasma diagnostics is presented that is based on real-time holographic interferometry. The hologram is used as a holographic optical element (HOE) that combines the properties of a hologram, of a lens, and of a grating simultaneously. The HOE is responsible for the formation of the interference pattern, and, in addition, acts as an imaging element and prevents most of the plasma radiation from reaching the interferogram detection system. The spectral and imaging properties of this HOE are calculated numerically, and this numeric procedure is tested experimentally. We applied the HOE-interferometry technique to the measurement of the electron density in a brightly radiating high-pressure xenon lamp. The principle of this experiment, two-wavelength interferometry, is described, and the results of the measurement are presented and discussed.

One of the main steps in establishing a phase diagram is finding the critical point data. Static steady state techniques for measuring of thermophysical properties of metals are limited to temperatures below about 2000 K. Fast dynamic resistive pulse heating experiments have been developed to permit the extension of the measurements to higher temperatures up to about 10000 K. Different experimental techniques are reviewed, which lead to a determination of critical point data for the metals lead, indium, zinc, iron and cobalt, using fast resistive pulse heating.