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.     

Deterimation of tensor polarizabilities in the perturbed 4snd 1 D 2 Ca Rydberg series

The tensor polarizabilities of the 4snd ¹ D ₂ Ca Rydberg states fromn=5 ton=19 have been measured using quantum beat spectroscopy at very low electric field strengths. The irregular behaviour of the polarizabilities is well reproduced by Coulomb approximation calculations. Using a quantum defect analysis, the strong variations of the tensor polarizabilities of themsnd ¹ D ₂ states of the alkaline earth atoms Ca, Sr, and Ba can be explained.     

Stark effect study of the 4f66s2 7 F 1, 2, 3, 4, 5, 6 levels of samarium using nonlinear level crossing technique

The nonlinear level crossing technique with parallel electric and magnetic fields was used to investigate the Stark effect of six levels of the ground multiplet 4f⁶6s^{2 7} F in the Sm I-spectrum. The tensor polarizabilities were deduced from the level crossing signals. The variation of the tensor polarizabilities of the levels of the ground multiplet is well reproduced by the LS coupling approximation, which gives an average value of α₂(F)=?0.88(6) kHz/(kV/cm)² for the six measured levels. The experimental results confirm the validity of the central field approximation in the ground configuration of Sm.     

Stark effect of hyperfine levels of the configuration 4f 7 (8 S) 6s6p in the europium I spectrum

The quadratic Stark effect in the hyperfine structure of all levels of the configuration 4f ⁷(⁸ S)6s6p in europium I, which can be excited by electric dipole radiation from the ground state, has been investigated by laser-atomic-beam spectroscopy. From the measured shifts and splittings of the hyperfine components the scalar and tensor polarizabilities have been deduced. From the polarizabilities radial integrals for electric dipole radiation were determined by a parametric analysis. With these radial integrals theoretical values of the polarizabilities were calculated.     

Natural radiative lifetimes in the2 S 1/2 and2 D 3/2, 5/2 sequences of neutral copper

Natural radiative lifetimes have been measured of the 3d ¹⁰ ns ² S _1/2 (n=6?10) and of the 3d ¹⁰ nd ² D _{3/2, 5/2} (n=5?9) sequences by using two step excitation of copper atoms in an atomic beam. The states investigated were populated by the light from two pulsed dye lasers pumped by the same Nd:YAG laser. The lifetimes of the² D sequence increase regularly with increasing principal quantum number. This is not the case for the² S series, because of configuration interaction in the² P series. In addition the lifetime of the 3d ¹⁰5p ² P _3/2 state has been measured together with its branching ratio.     

Systematic study of photoluminescence upon band gap excitation in perovskite-type titanates R1/2Na1/2TiO3:Pr (R=La, Gd, Lu, and Y)

Pr³⁺-doped perovskites R_1/2Na_1/2TiO₃:Pr (R=La, Gd, Lu, and Y) were synthesized, and their structures, optical absorption and luminescent properties were investigated, and the relationship between structures and optical properties are discussed. Optical band gap of R_1/2Na_1/2TiO₃ increases in the order R=La, Gd, Y, and Lu, which is primarily due to a decrease in band width accompanied by a decrease in Ti-O-Ti bond angle. Intense red emission assigned to f-f transition of Pr³⁺ from the excited ¹D₂ level to the ground ³H₄ state upon the band gap photo-excitation (UV) was observed for all compounds. The wavelength of emission peaks was red-shifted in the order R=La, Gd, Y, and Lu, which originates from the increase in crystal field splitting of Pr³⁺. This is attributed to the decrease in inter-atomic distances of Pr-O together with the inter-atomic distances (R, Na)-O, i.e., increase in covalency between Pr and O. The results indicate that the luminescent properties in R_1/2Na_1/2TiO₃:Pr are governed by the relative energy level between the ground and excited state of 4f² for Pr³⁺, and the conduction and valence band, which is primarily dependent on the structure, e.g., the tilt of TiO₆ octahedra and the Pr-Ti inter-atomic distance and the site symmetry of Pr ion.     

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.     

Crystal Structure and Electrical Conductivity of Palladium Sulfide BronzesMP3S4(M=La,Nd, and Eu)

Palladium sulfide bronzesMPd₃S₄(M=La, Nd, and Eu) were prepared in single phase. The bronzes are cubic with twoMatoms in (0,0,0; 1/2,1/2,1/2) and six palladium atoms in (1/4,0,1/2⥀) positions. The sulfur positions (x,x,x⥀) were determined with a guide of theRfactors. Thexvalues were 1/4 for La and Nd compounds (i.e., space groupPm3n), while a plot of theRfactors of EuPd₃S₄gave a very broad curve showing thexvalue rather displaced from 1/4. This result is considered to be associated with the mixed valency of europium (Eu²⁺and Eu³⁺) in this compound.MPd₃S₄(M=La, Nd, and Eu) exhibited metallic conductions with the electrical conductivities decreasing with increasing temperature in the experimental range from ∼15 K to room temperature. At 300 K, σ were 2.77, 2.42, and 2.28 S m⁻¹forMPd₃S₄(M=La, Nd, and Eu), respectively. From the Hall coefficient measurements, the carriers were found to be the electrons with their numbers 1.71, 1.68, and 0.82 per unit cell of the crystals ofM=La, Nd, and Eu compounds, respectively. These values suggest the formulas to beM³⁺(Pd²⁺₃e⁻)S²⁻₄for La and Nd compounds, and to be Eu²⁺_0.5Eu³⁺_0.5(Pd²⁺₃e⁻_0.5)S²⁻₄for Eu compound.     

Determination of the rate constants of the reactions of NO3 radical with CF3I and I(2P3/2)

The rate constant of the reaction of NO₃ radical with CF₃I was determined by a relative rate method using a Fourier transform infrared (FTIR) spectrometer smog chamber with a long path length gas cell. As a result, the upper limit of the rate constant was determined to be <2.2 × 10^?18 cm³ molecule^?1 s^?1 in 100 Torr of total pressure at 298 K, which suggests that CF₃I emitted into the atmosphere accumulates during night. The rate constant of the reaction of NO₃ with I(²P_3/2) was also measured using time‐resolved cavity ring‐down spectroscopy. The rate constant showed no pressure dependence in the range of 100–500 Torr of total pressure at 298 K and was determined to be (3.9 ± 1.0) × 10^?11 cm³ molecule^?1 s^?1. The present result is different from the previous ones and is about half of that reported most recently. From this rate constant, it is likely that the reaction of NO₃ radical with I(²P_3/2) does not have a much influence on the loss of I(²P_3/2) and the formation cycle of IO radical in the atmosphere. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 649–660, 2012     

The 4p 3 (2 P)ns,nd configurations of Se I

The photoabsorption spectrum of Se I has been photographed in the 1100–900 Å wavelength region, using a flash-pyrolisys system: about twenty lines were observed, most of them for the first time. With the support of Hartree-Fock calculations they have been identified and assigned to the 4p ⁴ → 4p ³ ns ³ P(n=7–14) and 4p ⁴ → 4p ³ nd ³ D(n=5–17) series, both converging on the limit 4p ³(² P _3/2).     

Crystal Structures and Magnetic Properties of 6H-Perovskites Ba3MRu2O9 (M=Y, In, La, Sm, Eu, and Lu)

Magnetic properties of quaternary oxides Ba₃MRu₂O₉ (M=Y, In, La, Sm, Eu, and Lu) are reported. Rietveld analyses of the X-ray diffraction data indicate that they adopt the 6H-perovskite structure and have the valence state of Ba₃M³⁺ Ru^4.5+₂O₉. All compounds are nonmetallic at least over the temperature range of 100-400 K. The magnetic susceptibilities show a broad maximum at 135-370 K except for the La compound, which shows a plateau around 22 K. In addition, another magnetic anomaly is observed at 4.5-12.5 K by the magnetic susceptibility and specific heat measurements for any compound. It is considered that this magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru₂O₉ dimer and to the magnetic interaction between the Ru₂O₉ dimers.     

Short-time quantum dynamics of the driven rigid rotor

Stark splitting of the barium 6snp ¹ P ₁ states with principal quantum numbers ranging from 8 to 15 and of the 5d7p ¹ P ₁ perturber level was measured in an atomic beam via pulsed laser excitation with time- and wave length-resolved fluorescence detection at low electric field strengths. Tensor polarizabilities were derived from the quantum beat signals observed in pure homogeneous electric fields. Strong variations of the tensor polarizabilities of the levels in the 6snp ¹ P ₁ series were found.     

Hyperfine structure in the configuration 4f 115d6s 2 of Er I

Hyperfine constants of low lying levels of the configuration 4f ¹¹5d6s ² in Er I have been measured for the only stable odd isotope,¹⁶⁷Er, using high resolution laseratomic-beam spectroscopy. Hyperfine parameters were evaluated from the experimental data using the effective tensor operator formalism. For this purpose eigenfunctions have been determined from an analysis of the fine structure energies of Er I as well as from ab initio multiconfiguration Dirac-Fock calculations. With the latter method also ab initio hyperfine constants for the levels investigated were evaluated. A comparison of calculated fine structure energies, Landég _J -factors and hyperfine constants with the experimental data allowed a test of the reliability of the fine structure and multiconfiguration Dirac-Fock wavefunctions. Effective nuclear electric quadrupole moments for¹⁶⁷Er have been determined from the experimental hyperfine constants using both calculated relativistic electronic radial integrals and hyperfine parameters for the 4f and 5d electrons in the configuration 4f ¹¹5d6s ² in Er I. From a comparison with the nuclear quadrupole moment measured in the mesic atom Sternheimer shielding factors are calculated. Configuration-interaction contributions to the radial integrals 〈r ^?3〉 _nl ⁰¹ of the 4f and 5d electrons have been determined.     

Preparation, XRD and Raman spectroscopic studies on new compounds RE2Hf2O7 (RE=Dy, Ho, Er, Tm, Lu, Y): Pyrochlores or defect-fluorite?

A series of compositions with the general formula RE₂Hf₂O₇ (RE=Dy, Ho, Er, Tm, Y and Lu) was prepared by a standard solid-state route and characterized by powder X-ray diffraction (XRD) and Raman spectroscopy. As per theoretical modeling reported in literature, some of these materials were predicted to exist in pyrochlore lattice. However, a careful X-ray diffraction, Raman spectroscopic and synchrotron radiation-XRD study revealed that under the experimental conditions used in the present investigation, out of all the RE₂Hf₂O₇ samples only Dy₂Hf₂O₇ has got a tendency to form a pyrochlore structure. All the other (Ho, Er, Tm, Lu, Y) hafnates crystallize in a defect-fluorite structure. In order to further ascertain these inferences, a few more RE₂Hf₂O₇ samples (La, Nd, Sm) i.e., with larger RE³⁺ ions were also prepared and the results were compared.     

Hyperfine structures and level isotope shifts of then 2 S 1/2 (n=7 – 12)- andn 2 D 3/2,5/2 (n=6 – 10)-levels of203,205Tl measured by atomic beam spectroscopy

Applying atomic beam laser spectroscopy, hyperfine constants as well as level isotope shifts of the (6s ² ns)² S _1/2 levels (n = 7 – 12) and (6s ² nd)² D _3/2,5/2 levels (n = 6 – 10) have been measured in²⁰³Tl and²⁰⁵Tl. Furthermore, some new hyperfine constants and level isotope shifts of the Tl² P _1/2,3/2-states are presented together with corrected results of earlier experiments. The hyperfine splittings have been compared with the predictions of the semiempirical theory. For theD-states a relatively poor agreement between these theoretical predictions and experimental results has been found. Using the experimental level isotope shifts and the δ〈r ²〉 value from muonic X-ray data, results of single-configuration Dirac-Fock calculations have been tested.     

Rare-earth cobalticyanides LnCo(CN)6·nH2O

Crystalline cobalticyanides LnCo^III(CN)₆·nH₂O with Ln = La,…, Lu, Y have been synthesized by a double-infusion technique. In analogy to the Cr and Fe compounds, the large rare-earth ions form a hexagonal modification while the smaller ions lead to the orthorhombic structure with 4H₂O. Experiments show that no magnetic ordering occurs down to 1°K. The Stark splitting of the J ground state due to the crystalline field is analyzed for the Ce and Sm compounds.     

Energy and polarization dependence of chemi-ionization processes inK(42 P 3/2)−K(42 P 3/2) collisions

Using crossed molecular beams we have investigated ionizing collisions between potassium atoms in their 4² P _3/2-states, leading to the exit channelsK ₂ ⁺ +e ^?,K ⁺+K ^?, andK(4² S _1/2)+K ⁺+e ^?, respectively. Measurements of the total ionization cross section as well as of the cross sections for the individual channels are reported as a function of both the relative collision energy (0.2 to 2.4 eV) and the angle between the electric field vector of the exciting laser light and the relative velocity vector. The results are interpreted in terms of the molecular states of theK ₂ ^* quasi molecule which are involved in the ionization process.     

Lifetime measurements of highly excited Rydberg states of strontium I

Lifetimes of Rydberg states of the triplet-series 5s ns ³ S ₁ withn = 19–23, 35 and 5s nd ³ D ₃ withn = 18–20, 23–28 in the spectrum of neutral strontium have been determined. Observation of the exponential decay after excitation by a pulsed laser in a fast atomic beam and subsequent state-selective field ionization was employed. The lifetimes of the states of the³ S ₁-series show the expectedn*³ dependence on the effective principal quantum number, while the³ D ₃-series is disturbed by configuration mixing. Furthermore, state re-populations induced by black-body radiation have been observed.     

Observation of forbidden (E2) lines in the ultraviolet spectra of Ca II,Sr II,and Ba II by inductively coupled plasma emission spectroscopy

Forbidden (electric quadrupole, E2) transitions of the type ns ²S_1/2–nd ²D_3/2 and ns ²S_1/2–nd ²D_5/2 in the ultraviolet spectra of singly ionized Ca, Sr, and Ba (with n = 4, 5 or 6 for Ca, Sr, and Ba, respectively) have been observed in the emission spectrum of an inductively coupled argon plasma. Wavelengths and wavenumbers of the six lines are reported and the values are in good agreement with those expected from literature data for the energy levels involved.     

Hydrolysis constants of tervalent lanthanum and lanthanide ions in 0.1 M KNO3 solution

The hydrolysis constants K _h of tervalent lanthanum and lanthanide ions at 25°C have been determined by pH titration against the background of 0.1 M KNO₃. pK _h values change monotonically from 8.53 for La(OH)²⁺ to 7.41 for Lu(OH)²⁺ and from 26.56 for La(OH)₃ to 21.43 for Lu(OH)₃.