Experimental and theoretical study of the hyperfine structure in the (5d+6s)96p configurations of Pt I

The hyperfine structure of the odd configurations 5d ⁹6p and 5d ⁸6s6p was studied with laser optogalvanic spectroscopy and high resolution interferometry in a platinum hollow cathode. A parametric hyperfine structure analysis for the configurations (5d+6s)⁹6p with 10 excited odd-parity levels was performed for¹⁹⁵Pt. We obtained one-electron hfs parameters,a _5d ⁰¹ =1160(320) MHz,a _6s ¹⁰ =35600(5300) MHz anda _6p ⁰¹ =1300(780) MHz for the configuration 5d ⁸6s6p. The corresponding $\left\langle {r^{ - 3} } \right\rangle _{nl}^{k_s k_l } $ values are compared with those known for other 5d-elements.     

On the hyperfine structure in the configurations 4f n 6s 2, 4f n 5d6s, 4f n 6s6p,and 4f n−15d6s 2 of the lanthanides

A survey of hyperfine analyses in the low-lying configurations 4f ⁿ 6s ², 4f ⁿ 5d6s, 4f ⁿ 6s6p, and 4f ^n?1 5d6s ² of the lanthanides is given. Experimental hf radial integrals 〈r ^?3〉 _nl ^kj are indicated for the configurations under investigation. From a comparison of experimental and theoretical hf radial integrals configuration-interaction contributions Δ _nl ^kj to the hfs have been evaluated for the configurations for which corresponding integrals were available. With nuclear electric quadrupole moments from muonic x-ray investigations and radial integrals 〈r ^?3〉 _nl ⁰¹ and 〈r ^?3〉 _nl ⁰² from experimental hfs quadrupole shielding correctionsR _nl ⁰¹ have been obtained. The variation of hyperfine radial integrals, configuration-interaction contributions and quadrupole shielding corrections over the 4f shell in the configurations under study is discussed. Trends of these quantities in different configurations are compared.     

Hyperfinestructure and isotope shift in the configuration 4f 7 6s8s of Eu I

The investigation of the isotope shift (IS) and hyperfine structure (hfs) is extended from Eu 4f ⁷ 6s7s to the complete configuration 4f ⁷ 6s8s, by means of the transitions 432.3, 456.5, 463.0 and 493.8 nm to 4f ⁷ 6s6p. A thorough experimental and theoretical analysis — including two further lines 492.8 and 498.7 nm from 4f ⁷ 5d ² — is carried out which e.g. confirms former fine structure calculations of one of us (J.F.W.) concerning some reclassifications. The discussion of the IS of the four levels (4f ⁷)6s8s with the sharing rule manifests again the need for inclusion of crossed-second-order effects. For the parameters we evaluated:g ₃(4f, 6s)=?1, 2(2) mK andd=79, 3(1.0) mK. The ratiog ₃/G ₃=?5, 9(1.0)·10^?6 is again in full agreement with those found by us in other Eu configurations. The single electron hfs splitting constantsa _4f ¹⁰ =?2, 3(4) mK,a _6s ¹⁰ =389(4) mK anda _8s ¹⁰ =49 (4) mK were also evaluated and compared to those found in 4f ⁷ 6s7s.     

Crossed-second-order-effects of the isotope shift and hyperfine-structure parameters in the Eu I configuration 4f 7 6s6d

In the Eu I configuration 4f ⁷ 6s6d the isotope shift (IS) and hyperfine-structure (hfs) of the termse ⁶ D ande ¹⁰ D were determined from fourteen transitions (4f ⁷ 6s6d-4f ⁷ 6s6p) with computer supported interference spectroscopy. From the IS of altogether nine levels of 4f ⁷ 6s6d the crossed-second-order-parameterg ₃(4f,6s)=?0.90(6)mK was evaluated. The ratiog ₃/G ₃=?4.4(3)·10^?6 (G ₃: Slater Integral of the fine structure) is of the same size as that from five other independent investigations and one theoretical value. The single electron hfs splitting constantsa _4f ¹⁰ =?1.9(3)mK,a _6s ¹⁰ =391(3)mK, anda _6d ¹² =0.9(3)mK were also evaluated and are compared with those of other Eu 4f ⁷ 6snl configurations.     

Fine structure and hyperfine structure in the excited configuration 5p 26s of the antimony I spectrum

By optical interference and VUV spectroscopy the doublet system of SbI 5p ²6s was investigated, so that now the hyperfinestructure of all 8 levels of 5p ²6s (A- andB-splitting constants) are known. From the analysis we receive a spin-orbit parameter ζ_5p =3,538(57) cm^?1 and from the hyperfine-analysis single electron splitting constantsa _5p ⁰¹ =52.4(4.6),a _5p ¹⁰ =?1.6(7.3),a _5p ¹² =72.3(2.3),a _6s ¹⁰ =91.7(4.1),b _5p ⁰² =?49.6(1.1) andb _5p ¹¹ =30.4(3.2) (all values in mK). For all calculations in the fs- and hfs-analysis the 5p ²6s ² D _3/2 has to be excluded (see discussion). With the figures given above the quadrupole moment¹²¹ Q(5p ²6s)=?0.44(3) barn was obtained. It is in good agreement with the¹²¹ Q(5p ³). For the core-polarization by the 5p electron in the innerfieldns-shells (n=1, 2, 3, 4, 5) and the unpaired 6s electron a field of +500(300) kG was obtained.     

Precision energies and hyperfine structures of the 5s5p 3 P 0,1,2 0 and 5s6s 3 S 1 levels in In II

Absolute frequencies of hyperfine components of the 230.6 nm (5s ^{2 1} S ₀?5s5p ³ P ₁ ⁰ ), 193.6 nm (5s5p ³ P ₀ ⁰ ?5s6s ³ S ₁), 197.7 nm (5s5p ³ P ₁ ⁰ ?5s6s ³ S ₁) and 207.9 nm (5s5p ³ P ₂ ⁰ ?5s6s ³ S ₁) transitions in In II emitted from a hollow-cathode source have been measured using a high-resolution, scanning échelle monochromator. The measured frequencies of these four transitions have been used to determine the energies and hyperfine interaction constants of the 5s5p ³ P ₀ ⁰ ,³ P ₁ ⁰ ,³ P ₂ ⁰ and 5s6s ³ S ₁ levels in In II. The hyperfine interaction constants for the dominant isotope¹¹⁵In are found to be: 5s5p ³ P ₁ ⁰ A=0.2322(2) cm^?1,B=?0.0159(9) cm^?1 5s5p ³ P ₂ ⁰ A=0.1699(4) cm^?1,B= 0.021 (6) cm^?1 5s6s ³ S ₁ A=0.4022(4) cm^?1,B= 0.002 (2) cm^?1. The absolute frequency of the very narrow, strongly forbidden In II 236.5 nm (5s ^{2 1} S ₀?5s5p ³ P ₀ ⁰ ) transition, which has been proposed as a candidate for a new optical frequency standard, is found to be 42275.986(7) cm^?1.     

Ab initio study of small He cluster ions He n + ,n=2, 3, 4, 5, and low-lying Rydberg states of He4

SCF and CEPA calculations are applied to study the structure of small He cluster ions, He _n ⁺ ,n=2, 3, 4, 5 and some low-lying Rydberg states of He₄. The effect of electron correlation upon the equilibrium structures and binding energies is discussed. He ₃ ⁺ has a linear symmetric equilibrium geometry with a bond length of 2.35a ₀ and a binding energyD _e =0.165 eV with respect to He ₂ ⁺ +He (experimentally:D ₀=0.17 eV which corresponds toD _e ≈0.20 eV). He ₄ ⁺ is a very floppy molecular ion with several energetically very similar geometrical configurations. Our CEPA calculations yield a T-shaped form with a He ₃ ⁺ centre (R _e = 2.35a ₀) and one inductively bound He atom (4.39a ₀ from the central He atom of He ₃ ⁺ ) as equilibrium structure. Its binding energy with respect to He ₃ ⁺ +He is 0.031 eV. A linear symmetric configuration consisting of a He ₂ ⁺ centre with a bond length of 2.10a ₀ and two inductively bound He atoms (4.20a ₀ from the centre of He ₂ ⁺ ) is only 0.02–0.03 eV higher in energy. We expect that in larger He cluster ions structures with He ₂ ⁺ and He ₃ ⁺ centres andn?2 orn?3 inductively bound He atoms have nearly the same energies. In He₄ a low-lying metastable Rydberg state (³ Π symmetry for linear He ₄ ^* ,³ B ₁ for the T-shaped form) exists which is slightly stronger bound with respect to He ₃ ^* +He than the corresponding ion.     

Hyperfine structure in the configuration 4f 136s7s of Tm I

Doppler-free saturation absorption spectroscopy was applied on an atomic thulium vapour in a see-through hollow cathode for the determination of precise values for the magnetic dipole hyperfine structure constantsA of 6 levels of the configuration 4f ¹³ 6s7s. A parametric analysis of the hyperfine structure has been performed, using wave-functions from a fine structure calculation, which leads to one-electron hyperfine structure parametersa _4f ⁰¹ =?500(6) MHz,a _6s ¹⁰ =?5058(47) MHz, anda _7s ¹⁰ =?1012 MHz.     

Intensités des transitions optiques de [PtCl4]2−

The oscillator strengths of the “d-d” transitions of the ion [PtCl₄]^2? were calculated. The method, based on the evaluation of the MO of the distorted ion, gives results in good accordance with the experimental data. The transition to ¹ B _1g (a _1g →b _1g ^* ), as a consequence of the participation of the orbital 6s, mixed with \(5d_{z^2 } \) in \(a_{1_g } ,a_{1_g } \) is characterized by a very low intensity in the case of thex,y polarization.     

Hyperfine structure of the 4f 7 (8 S 0) 6s 7 S 3 0 level in151,153Eu II by fast ion beam — laser spectroscopy

The hyperfine structure (hfs) of the level 4f ⁷(⁸ S ⁰) 6s ⁷ S ₃ ⁰ in^151,153Eu II has been measured with collinear fast ion beam — laser spectroscopy. The hfs of the⁷ S ₃ ⁰ level has been measured with interferometric methods previously but, to our knowledge, this is the first measurement with the laser ion beam technique. In the present experiment the hfs of the 4f ⁷(⁸ S ₇ ^2/0 ) 6p _1/2 levels were also obtained. Corresponding magnetic dipole and electric quadrupole coupling constantsA andB are evaluated.     

Resonant and Off-resonance ionization of laser-excited sodium vapor

Electrons produced in a sodium effusive beam irradiated by pulsed laser light have been energy-analyzed. For resonant excitation of the atoms to the 3p state, we have studied associative ionization of excited Na(3p) (AI), Penning ionization (PI) and photoionization of highly-excited Na(n l),n l=3d, 4p, 5s, 4d/4f, by measurements of electron energy spectra. Our interpretation of the spectra is supported by a numerical analysis of the data which leads to estimates of the cross sections compatible with values previously measured in other experiments. Off-resonance ionization is considered at a particular wavelength. It is presumed to involve laser-excited dimers Na ₂ ^** . Spectra show that highly-excited atoms are produced by photodissociation of Na ₂ ^** or from Na ₂ ^** -Na collisional energy transfer, and that these atoms support the dominant off-resonance ionization channel in our laser excitation conditions.     

Spectroscopic properties of the Ar 2 * (5p) excimer states

The transitions between Ar ₂ ^* (5p) and Ar ₂ ^* (4sΣ _u) have been investigated by absorption spectrometry. The fine structure of the Ar ₂ ^* (5p ³ Π _g) was attributed to a predominantly Hund’s case a coupling. A spin orbit coupling constant of A = (9.8±0.3) cm^-1 results. Absorption by the singlet system allows one to determine the triplet/singlet splitting between the Ar ₂ ^* (4s Σ _u) states to be (540 ± 100) cm^-1. The transition probabilities of the Ar ₂ ^* (5p) and Ar ₂ ^* (6p) levels were determined by saturation spectrometry yielding values between (0.2–2.5) · 10⁶ s^-1.     

Ab initio MRD-CI study of neutral and charged Ga2, Ga3 and Ga4 clusters and comparison with corresponding boron and aluminum clusters

MRD-CI calculations were performed on Ga, Ga₂, Ga₃, Ga₄ and on the corresponding positive and negative ions. In general, pseudopotentials were used, and 4s4p/2s2p basis sets withs andp diffuse functions and one or twod functions. For Ga₂, all-electron calculations were also performed. For Ga ₂ ^(±) , potential functions for ground and low-lying excited states are given. For Ga ₃ ^(±) , geometries were optimized both inC _2v andD _∞h symmetry. The lowest state of Ga ₃ ⁺ is found to be¹Σ _g ⁺ , of Ga₃ ⁴ A ₂, and of Ga ₃ ^{? 1} A ₁ (D _3h ). Ionization potentials and electron affinities of Ga₃ were evaluated. Many low-lying excited states of Ga ₃ ^(±) were found. Rhombic (D _2h , including squareD _4h ), tetrahedral (T _d ), T-shaped (C _2v ) and linear structures (D _∞h) were investigated in the search for the lowest state of Ga₄. A square-planar arrangement of the nuclei, withR _e = 5.30 a₀, was found to have the lowest energy. The other geometries lie about 0.5 eV higher. InD _2h symmetry, low-lying excited states of Ga₄, as well as ground and excited states of Ga ₄ ⁺ and Ga ₄ ^? were studied. Geometries, ionization potentials, electron affinities, atomization and fragmentation energies of Ga _n are compared with corresponding data for B _n and Al _n . Typical changes in going from first-row to third-row atoms are observed.     

Reactivity of positively charged cobalt cluster ions with CH4, N2, H2, C2H4, and C2H2

Reactivity of positively charged cobalt cluster ions (Co _n ⁺ ,n=2?22), produce by laser vaporization, with various gas samples (CH₄, N₂, H₂, C₂H₄, and C₂H₂) were systematically investigated by using a fast-flow reactor. The reactivity of Co _n ⁺ with the various gas samples is qualitatively consistent with the adsorption rate of the gas to cobalt metal surfaces. Co _n ⁺ highly reacts with C₂H₂ as characterized by the adsorption rate to metal surfaces, and it indicates no size dependence. In contrast, the reactions of Co _n ⁺ with the other gas samples indicate a similar cluster size dependence; atn=4, 5, and 10?15, Co _n ⁺ highly reacts. The difference can be explained by the amount of the activation energy for chemisorption reaction. Compared with neutral cobalt clusters, the size dependence is almost similar except for Co ₄ ⁺ and Co ₅ ⁺ . The reactivity enhancement of Co ₄ ⁺ and Co ₅ ⁺ indicates that the cobalt cluster ions are presumed to have an active site for chemisorption atn=4 and 5, induced by the influence of positive charge.     

A theoretical study of internal rearrangements and open channels for fission and mass exchanges in Xe n + clusters

In a previous work the equilibrium geometrical and electronic structures of Xe _n ⁺ clusters had been established using a non-empirical model hamiltonian. The same model is used to determine the energetic barriers between the nearly degenerate isomers; the movement of the neutral atoms around the Xe ₃ ⁺ or Xe ₄ ⁺ ionized linear cores are quite easy (ΔE?0.9 kcal/mole), the changes from a Xe ₃ ⁺ to a Xe ₄ ⁺ core are more difficult (ΔE?2.0 kcal/mole). The energetically possible fissions from a vertical photoionization \(Xe_n \xrightarrow{{h v}}Xe_n^{v + } \to Xe_p^ + + Xe_{n - p} \) forn≦19,p=1–9 and 12–14 and mass exchanges Xe _p ⁺ +Xe _q →Xe _p+m ⁺ +Xe _q?m (m=1,2,3) from relaxed Xe _p ⁺ clusters are given forp+m≦9 and 12–14 andq≦19. Surprisingly the reverse reactions are shown to occur for some values ofp andq. Numerous processes lead to Xe ₁₃ ⁺ , which is especially stable.     

Interpretation of experimental Mössbauer quadrupole splittings of iron pentacyanide complexes using molecular orbital theory

Semiempirical self-consistent-field molecular-orbital calculations are carried out for six iron-pentacyanide complexes and are used to interpret their experimental Mössbauer quadrupole splittings. Probable orientations are identified for the C₆H ₅ ^? and NO ₂ ^? groups in Fe(CN)₅NOC₆H ₅ ^?3 and Fe(CN)₅NO ₂ ^?4 . Calculations on Fe(CN)₅NO^?2 and Fe(CN)₅NO^?3 can simultaneously be brought into agreement with experiment by reparametrization to make the NO group more positively charged. All the calculations indicate the importance of including all the Fe 3d and 4p orbitals in the calculations and of considering neighboring-atom effects.     

Lifetime measurements of the 2p 3d 3 D 1, 2, 3 0 and 2p 3d 1 P 1 0 levels in NII by beam-foil-laser spectroscopy

Accurate lifetimes measured by means of the cascade-free method based on laser excitation of a fast ion beam preexcited in a carbon foil are reported for four 2p 3d levels in NII. The lifetime results are: τ(2p 3d ³ D ₁ ⁰ )=0.209±0.007 ns, τ(2p 3d ³ D ₂ ⁰ )=0.219±0.007 ns, τ(2p 3d ³ D ₃ ⁰ )=0.217±0.005 ns, and τ(2p 3d ¹ P ₁ ⁰ )=0.410±0.017 ns. These results are compared to theoretical and experimental lifetimes reported previously.     

Guided ion beam studies of the reactions of O+, O 2 + , N+ and N 2 + with silane

Guided ion beam mass spectrometry is used to measure the cross sections as a function of kinetic energy for reaction of SiH₄ with O⁺(⁴S), O ₂ ⁺ (²Π_g,v=0), N⁺(³P), and N ₂ ⁺ (²Σ _g ⁺ ,v=0). All four ions react with silane by dissociative charge-transfer to form SiH _m ⁺ (m=0?3), and all but N ₂ ⁺ also form SiXH _m ⁺ products where (m=0?3) andX=O, O₂ or N. The overall reactivity of the O⁺, O ₂ ⁺ , and N⁺ systems show little dependence on kinetic energy, but for the case of N ₂ ⁺ , the reaction probability and product distribution relies heavily on the kinetic energy of the system. The present results are compared with those previously reported for reactions of the rare gas ions with silane [13] and are discussed in terms of vertical ionization from the 1t ₂ and 3a ₁ bands of SiH₄. Thermal reaction rates are also provided and dicussed.     

The thermodynamic parameters of oxygen nonstoichiometry defects in lanthanum cobaltite doped with acceptor impurities (Sr and Ni)

The oxygen nonstoichiometry δ of lanthanum cobaltite doped with acceptor impurities (Sr and Ni), La_{1 ? x} Sr_xCo_0.9Ni_0.1O_{3 ? δ} (x = 0.1, 0.3), was studied by high-temperature thermogravimetry over the temperature and pressure ranges 723 K ≤ T ≤ 1373 K and 10^?3 atm ≤ $p_{O_2 } $ ≤ 1 atm. The partial replacement of cobalt with nickel and lanthanum with strontium increased the oxygen nonstoichiometry δ. The partial molar enthalpies $\Delta \bar H^\circ _O $ and entropies $\Delta \bar S^\circ _O $ of solution of oxygen in the solid phase were calculated. Models of point defect formation were suggested and analyzed. The equilibrium constants of formation and concentrations of predominant point defects, ionized oxygen vacancies V _o ^.. , holes Me _Co ^. (Co _Co ^. and Ni _Co ^. ), and electrons Me _Co ^′ (Co _Co ^′ and Ni _Co ^′ ) localized on 3d transition metals, were determined by nonlinear regression from the experimental and theoretical logp $p_{O_2 } $ ?δ dependences.