Tensor polarizabilities of the 4f 7(8 S)5d6s 2 9 D 2,3,4,5,6 levels in Gd I

The optical pumping method with rf detection and the nonlinear level crossing technique were used in parallel electric and magnetic fields to investigate the Stark splitting of all the fine structure levels of the ground multiplet 4f ⁷ (⁸ S) 5d6s ^{2 9} D in Gd I. The tensor polarizabilities were deduced from the level crossing and the rf signals. The variation of the tensor polarizabilities is well reproduced by the LS coupling approximation, except for the small value of the⁹ D ₅ level. A value of the tensor polarizability of the 5d electron is evaluated from the experimental results, ₂(5d)=2.00(6) kHz(kV/cm)². It is shown that the ratio between the electric quadrupole constant and the tensor polarizability is constant, except for the⁹ D ₅ ratio, which is caused by a breakdown of the central field model.     

Zeeman effect of superfluorescently populated 6snf 1F3 Ba I levels

Zeeman quantum beats of the Ba I 6snf ¹F₃ levels were measured between n=10 and 19 by time resolved recording of the exponential decay of the fluorescence on the 6snf ¹F₃ — 6s5d ¹D₂ transitions. The 6snf ¹F₃ levels were populated by superfluorescence pulses from the energetically higher lying 6s(n + 3)d ¹D₂ levels, the ¹D₂ levels were excited in a resonant two step process by two pulsed dye lasers. The experimental results of the g _J values in the 6snf ¹F₃ sequence are in fair agreement with the prediction of multi-channel quantum-defect theory.     

Switching from "absorption within transparency" to "transparency within transparency" in an electromagnetically induced absorption dominated transition

The absorption of a resonant coupling laser driving a closed degenerate two-level system in an atomic cesium beam was investigated as a function of the detuning of a second laser probing the same transition. The measurements were performed for four different polarization combinations of the two laser beams. Except for the beams of counterrotating polarizations all coupling-laser absorption profiles showed "absorption within transparency," i.e., the absorption in the region around the two-photon resonance was smaller than the absorption corresponding to the one-photon transition induced by the coupling laser, and an extra absorption peak was observed on this curve at the two-photon resonance. With regard to the beams of counterrotating polarizations we observed a switch from absorption within transparency to "transparency within transparency" when the probe-laser power exceeded the constant coupling-laser power. In other words, the cesium ensemble became mostly transparent to the coupling-laser beam at the two-photon resonance.     

Radiative lifetimes of superradiant populated Ba Rydberg levels

Radiative lifetimes of 6s7f¹F₃, as8f¹F₃, and 6s9d¹D₂ Ba Rydberg levels were measured in an atomic beam by time resolved recording of the exponential decay of the fluorescence. The excitation was performed by use of two pulsed dye lasers and a superradiant emission or a superradiant cascade controlled by a cavity.     

On the tensor polarizabilities in the 4f N 6s 2 ground levels of the neutral rare-earth atoms

A systematic study of the Stark splitting of the 4f ^N 6s ² ground levels in the lanthanides was performed by the nonlinear level-crossing technique and the optical pumping method with rf detection in parallel electric and magnetic fields. The tensor polarizabilities of the hyperfine structure levels in¹⁴¹Pr I,¹⁵⁹Tb I,¹⁶⁵Ho I,¹⁶⁹Tm I and of the fine structure levels in¹⁴²Nd I,¹⁶⁴Dy I, and¹⁶⁶Er I were deduced from the level-crossing and rf signals. Values of the tensor polarizability of the 4f electron were evaluated from the experimental results. On average these values decrease with the increasing number of 4f electrons from the value of¹⁴¹Pr (4f ³ 6s ²) α₂(4f)=1.16(12) kHz/(kV/cm)² to the value of¹⁶⁹Tm (4f ¹³6s ²) α₂(4f)=0.68(4) kHz/(kV/cm)². This decrease is caused by the lanthanides contraction.     

Stark effect investigations of the 4f 14 6s 6p 3 P 1 and1 P 1 levels of ytterbium

The tensor polarizabilities of the 4f ¹⁴ 6s 6p ³ P ₁ level were investigated for all stable Ytterbium isotopes by the method of optical double resonance. The tensor polarizabilities were deduced from the rf-resonance signals in parallel electric and magnetic fields. The value obtained for the even Yb isotopes is in good agreement with the results derived from the measurements on the odd isotopes. The mean value isα _ten(³ P ₁)0=5.99(34)kHz/(kV/cm)². The tensor polarizability of the 4f ¹⁴ 6s 6p ¹ P ₁ level of¹⁷¹Yb was measured by means of the level crossing technique with parallel electric and magnetic fields. The experimental result isα _ten(¹ P ₁)=?14.3(1.4)kHz/(kV/cm)². This is compared with the prediction of the LS coupling approximation using the experimental data of the³ P ₁ level. Only poor agreement is obtained which is due to the configuration mixing in the¹P₁ level.     

Spectral measurement of the caesium D(2) line with a tunable heterodyne interferometer

The optical properties of a caesium atomic beam driven on a resonant hyperfine transition in the D(2) line were studied as a function of the probe laser frequency. Using a third off-resonant laser system, a heterodyne interferometer allowed simultaneous absorption and phase shift measurements of either the probe or the coupling laser. The signal features of the probe and coupling laser transmitted intensities showed strong differences in the vicinity of the hyperfine transitions excited by the probe laser. Regular absorption signals and electromagnetically induced transparency were found in either transmitted intensities. Furthermore, light induced birefringence of the probe laser was measured.     

Magnetic field-induced ΔF=±2,3,4 transitions in the Eu I-spectrum

The occurrence of ΔF=±2, ±3, and ±4 transitions in the hyperfine structure of the Eu I lineλ 629.1 nm (4f ⁷6s ² a ⁸ S _7/2?4f ⁷6s6p z ⁸ P _5/2) was investigated with the application of high-resolution laser-atomic-beam spectroscopy. It was possible to show that the appearance of such transitions depends on the magnitude of an external magnetic field. Calculations of the hyperfine Zeeman splittings of the excited and the ground state were performed. This allowed the identification of the forbidden transitions.     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery.