Isotope and hyperfine splittings for two UV transitions in tungsten I by saturation and polarisation spectroscopy

Isotope shifts and hyperfine splittings in tungsten I have been measured by Doppler-free saturated absorption and polarisation spectroscopy on two UV transitions at 294.44 nm and 294.70 nm. The splittings between the even isotopes (¹⁸²W, ¹⁸⁴W, ¹⁸⁶W) and the splitting between the two strong hyperfine components of ¹⁸³W were measured in a natural isotopic mixture of tungsten introduced into a hollow cathode discharge. In addition, using single isotope ¹⁸³W, the level hyperfine splittings were measured by resolving crossover peaks between the strong and weak hyperfine components. These measured level splittings are compared with those predicted from centre of gravity considerations.     

Picosecond saturation spectroscopy in microemulsions

We report on a first application of picosecond spectroscopy in the field of microemulsions. First results are given about the reorientation and absorption recovery kinetics of DODCI localized in the core of inverted micelles containing methanol. The experimental technique is the Absorption Saturation. The isotropic and anisotropic parts of the saturated absorption are detected with a time resolution of a few picoseconds.     

The tilted-multifoil hyperfine interaction and nuclear spectroscopy

Ions emerging from a stretched foil with their velocity vectorv at an oblique angle to the normaln (tilted foil geometry) are known to be polarized along the axisv×n. The electronic polarization of atomic configurations can influence the nucleus during flight in vacuum via the hyperfine interaction. For a large number of polarizing foils and for very short interaction times, the resulting effects resemble a pure precession in an external magnetic field and have been used to measureg-factors of short-lived nuclear high-spin levels. For long interaction times, a net nuclear polarization is induced and has so far been utilized to determine signs of nuclear quadrupole moments of high-spin isomers and to investigate parity nonconservation effects in⁹³Tc.     

Observation of nonstationary effects in saturation spectroscopy

We have studied the nonstationary effects in saturated absorption spectroscopy of the ⁸⁷Rb D₂ line. Varying the size of the σ⁺ polarized pump laser beam, we observed saturated absorption spectra for the σ^± polarized probe beam. For equal polarizations of the pump and probe beams, we found that the resonance signal for the F_g = 1 → F_e = 2 line, and the crossover lines between F_g = 1 → F_e = 2 and F_g = 1 → F_e = 1 (and 0) lines increased to a greater extent than the others. This observation can be understood from the calculated time evolution of the populations of the ground-state sublevels by means of a rate equation model. We also compared experimental data for other conditions with the calculated results. We found good agreement between the calculated results and the data.     

Unidirectional saturation spectroscopy,II

The general probe absorption coefficient derived in Part I is specialized to homogeneous- and inhomogeneous-broadening limits and illustrated as the dipole lifetime is increased from 0 to values comparable to the level lifetimes. This progression reveals the relation between pulsation dips of the short-dipole lifetime limit and the dynamic Stark effect in general. Interpretations of the coherent interactions involved are given in terms of modulator and Raman effects and of dressed atoms. The single-probe unidirectional pulsation dip is shown to be a special case of the grating dip in which the fringe spacing becomes infinite. Analogies with three-level systems are given in which both two and three-level cases are seen to obey an “equal-area theorem”, and to involve level crossing. Some comparison is made with corresponding spectroscopy in which spontaneous emission provides the probe radiation. Work performed as a Humboldt awardee in Germany. Work supported in part by the Space and Missiles Systems Organization, Los Angeles, California. Work supported by the Deutsche Forschungsgemeinschaft     

Concepts for the measurement of hyperfine structure in EPR spectroscopy

Continuous wave and pulsed EPR methods for the measurement of hyperfine interactions are reviewed.     

Laser Stark saturation spectroscopy in methyl alcohol

The method of Lamb dip spectroscopy in Stark tuned molecular gases is discussed and applied to the experimental assignment of methyl alcohol infrared transitions in the ₅ C–O stretch band. Theoretical expressions for Stark Lamb dip patterns are derived for P, Q and R-branch transitions. Stark tuning results and transition quantum number assignments are presented for several 10m transitions, along with measured values of resonant frequencies, absorption coefficients and pressure broadening coefficients.Work supported by the Army Research Office, Durham, and the National Science Foundation.     

Laser spectroscopy applied to the study of hyperfine interactions

The impact of laser-spectroscopy techniques on the study of hyperfine interactions is illustrated by chosen examples. A brief survey of the theory of hyperfine interactions is given as well as an overview of the available experimental techniques. Results from alkali atoms, alkaline-earth elements and Group III atoms are given with special emphasis on the studies of electronic properties in sequences of Rydberg states and the investigation of nuclear properties for long chains of isotopes of the same element. Recent developments on the theoretical side, particularly what regards the many-body perturbation approach, are also discussed.     

2D-REFINE spectroscopy: separation of overlapping hyperfine spectra

We show on a mixture of three spectrally overlapping paramagnetic compounds TEMPO, BDPA and CuHis that it is possible to separate their field-swept and hyperfine spectra based on the difference in their longitudinal relaxation times T1. This was achieved in a two-dimensional experiment, where one dimension corresponds to the spectral domain and the second dimension encodes the relaxation behavior of the individual compound. Inverse Laplace Transform with respect to this domain separates the field-swept and hyperfine spectra of the individual compounds in the relaxation rate domain. This extends our formerly proposed Relaxation Filtered Hyperfine (REFINE) method to be applicable to more than two spectrally overlapping spectra by adding a further dimension to the chosen EPR experiment.     

Experimental method for the measurement of hyperfine transition saturation intensities in a gaseous medium

A laser system capable of generating picosecond pulses of 2 ps duration and peak powers of up to 50 MW, tunable throughout the emission spectrum of the lasing medium is described. The system consists of a cw dye laser which is tuned and is actively mode-locked by means of a novel interferometer. Single-pulse amplification is achieved via a two-stage N₂-laser-pumped amplifier arrangement. One of the most attractive features of the system here described is its inherent versatile broad tunability, which should allow, with different lasing media and pump sources, ps pulse generation from 400 to 700 nm using the same interferometer device.     

Xenon saturation spectroscopy by diode laser

Summary Commercial diode lasers have emission wavelengths which overlap some absorption xenon lines. We have performed saturation spectroscopy of four lines, leaving from the first excited atomic configuration 5p ⁵6s, at 823.16 nm, at 828.01 nm, at 834.68 nm and at 820.63 nm, in a weak glow discharge of natural xenon. Natural xenon is a mixture of several isotopes, and the two even isotopes, Xe(129) (26% of relative abundance) and Xe(131) (21%), have a nuclear spin (1/2 and 3/2, respectively) that produces a hyperfine structure. The complex resulting spectra have been resolved and the results are compared with the available literature data. The authors of this paper have agreed to not receive the proofs for correction.     

Microwave spectroscopy measurements of the hyperfine structure in antiprotonic 3He

We shall present here the first experimental results for microwave spectroscopy of the hyperfine structure of antiprotonic He-3 and a comparison to numerical simulations of the measurement. Due to the helium nuclear spin, antiprotonic He-3 has a more complex hyperfine structure than antiprotonic He-4 which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. The comparison of measured data to simulations allows to investigate the collisional processes between the helium atoms of the target medium and the antiprotonic helium atomcules. The collision rates can not be calculated exactly, but estimated by comparison of numeric simulations with the experimental results. Two out of four super-super-hyperfine (SSHF) transition lines of the (n, L)?=?(36, 34) state were observed. The measured frequencies of the individual transitions are 11.12559(14)?GHz and 11.15839(18)?GHz, less than 1?MHz higher than the current theoretical values, but still within their estimated errors. The frequency difference between the two lines also agrees with theoretical calculations.     

Optical saturation in the photothermal spectroscopy of fluorescent materials

The dependence of the fundamental and harmonic photothermal (PT) signal on the intensity I ₀ of the illumination source is analyzed. It is shown that both components of the PT signal do not increase indefinitely with I ₀, but at sufficiently high power densities begin to decrease as 1/I ₀. Along with photoacoustic saturation, this defines an upper limit for the sensitivity of spectrometers based on PT detection.     

Acoustic spectroscopy of fluid saturation effects in carbonate rock

The results of acoustic spectroscopy of a carbonate sedimentary rock in the case of saturation degree variations are given. The data on the elasticity and dissipation tensors within a two-octave range are obtained for one and the same sample using one and the same measurement technique. High accuracy of the measurements allowed distinguishing all three saturation stages, namely, condensation, meniscus creation, and pore filling with a fluid. The observed variations are in good agreement with the results of a standard granulometric analysis. The character of variations in the frequency dependence of attenuation coefficients make it possible to make reasonable assumption concerning the mechanisms responsible for acoustic energy absorption in porous materials.