Ni XXVII THEORETICAL SPECTRUM (original) (raw)
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Term analysis of the system 3d6−3d54p of the fifth spectrum of nickel (Ni V)
Physica B+C, 1976
The spectrum of Ni V has been measured in the region from approximately 300 A to 450 A where the transitions between the 3d6-3d54p configurations have been located. Out of the 34 theoretically possible levels of the 3d 6 configuration 33 levels have been determined, only the higher 1S o level is missing. Out of the 214 levels of the 3d54p configuration 177 levels are known. All these level values and the classified lines are tabulated at the end of this paper. Parametric (configuration) calculations of the levels of the 3d 6 and 3d54p configurations have been made.
Band-structure calculations for Ni
We present a self-consistent calculation of the electronic structure of different nickel hydrides based on the linear-muffin-tin-orbital formalism and using the local-density approximation for the exchange and correlation. The calculations for the ground state show a continuous decrease of the saturation magnetization of Ni by increasing the hydrogen concentration as a result of changes in the exchange-splitting parameter and in the Fermi energy. The presence of hydrogen in the Ni matrix modifies the electronic states of the bulk. New impurity states appearing far below from the d band of the host are found in agreement with photoemission measurements. The density of states at the Fermi level increases as a function of the hydrogen concentration, giving in this way a greater y coefficient for the electronic specific heat than that of pure Ni. The equilibrium lattice parameter of the various Ni hydrides also increases as a function of the hydrogen concentration, reaching a saturation value for a concentration of approximately 75 at. %. All features calculated are supported by experiments, and our first-principles calculation explains the increase of the electronic specific heat together with the loss of the ferromagnetism. We also found that the electronic density around the proton occupying the octahedral sites in the fcc Ni matrix is larger than that in the free atomic hydrogen. The electron transfer occurs from the Ni atoms to the hydrogen. The polarization of H in Ni is directed opposite to the bulk polarization and of the same order of magnitude as for positive muons in the same matrix. The hyperfine field of muon in Ni can be derived by use of the calculated values for the spin density around the proton and by taking into account the zero-point motion of the positive charge around its equilibrium position.
Ni2 revisited: Reassignment of the ground electronic state
The Journal of Chemical Physics, 1995
Resonant two-photon ionization spectroscopy was used to study jet-cooled Ni 2 produced by pulsed laser ablation of a nickel target in the throat of a supersonic nozzle using argon as the carrier gas. Spectral regions previously investigated using helium as the carrier gas were reinvestigated, and the improved cooling achieved was found to suppress transitions arising from an ⍀ϭ4 state that had been thought to be the ground state. Seven new vibronic progressions were assigned, with spectroscopic constants determined for the excited states. The predissociation threshold in Ni 2 was reinvestigated, and a revised value for the binding energy is given as D 0 ؠ ͑Ni 2 ͒ϭ2.042Ϯ0.002 eV. The ionization energy of Ni 2 was found to be 7.430Ϯ0.025 eV, and from this result and the revised bond dissociation energy of the neutral, the binding energy of the cation was calculated to be D 0 ؠ ͑Ni 2 ϩ ͒ϭ2.245Ϯ0.025 eV. Similarly, D 0 ؠ ͑Ni 2 Ϫ ͒ϭ1.812Ϯ0.014 eV is obtained using D 0 ؠ ͑Ni 2 ͒ and the electron affinities of Ni and Ni 2. Twenty bands were rotationally resolved, all originating from a lower state of ⍀Љϭ0 g ϩ or 0 u Ϫ which we argue is the true ground state, in agreement with ligand field and ab initio theoretical studies. The rotational analysis also yielded a ground state bond length of 2.1545Ϯ0.0004 Å for 58 Ni 2 .
Energy levels and radiative rates for optically allowed and forbidden transitions of Ni XXV ion
Astronomy and Astrophysics, 2008
Aims. We report calculations of energy levels and radiative rates for 1300 fine-structure levels generated from 189 configurations of Be-like Nickel. Methods. The General Purpose Relativistic Atomic Structure Program (GRASP2), developed by the I P Grant group in 1989 and partly improved by our group, is adopted in the calculations of energy levels and radiative rates. Results. Our calculations are compared with those of other numerical methods and experiments so that their accuracy can be assessed. Additionally, the wavelengths, oscillator strengths, and radiative rates (for a given radiative rate and level structure, it is then easy to derive the line strength) are reported for all electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) transitions among these levels. Finally, the lifetimes of all excited levels are reported.
MVV super Coster–Kronig spectra of nickel near the excitation threshold
Journal of Physics: Condensed Matter, 2005
The MVV super Coster-Kronig (sCK) spectra of metallic Ni have been measured near the 3p excitation threshold by varying excitation photon energy. The results have been interpreted on the basis of the Cini-Sawatzky theory. The measured sCK band has composite structure with features at electron kinetic energy of 49.8 eV, 56.3 eV, 59.5 eV, and 60.5 eV. If we interpret the band at 49.8 eV to be the split-off quasi-atomic band, we can estimate the effective intra-atomic Coulomb energy at a large value of 8 eV. The spectral shape of the MVV sCK band measured by excitation with vacuum ultraviolet light does not coincide with that obtained by the Mg Kα excitation nor with that of the L 3 VV Coster-Kronig band. The shape of the MVV sCK spectrum changes as excitation energy changes. The excitation-energy range in which such spectral change occurs extends from the 3p threshold to 10 eV above it. As the kinetic energy for the MVV sCK band starts to overlap that of the two-hole-boundstate band, the MVV sCK band changes its shape considerably and the two spectra get inseparable. In this excitation-energy region, the spectator electron excited optically forms a virtual bound state with the two 3d holes. The location of the apparent twohole-bound-state band shifts toward high binding energy on the 3p-3d resonance. This can be interpreted as a kind of the final state interaction. The suggested intermediate and final states of the single step transition are consistent with the constant-initialstate spectra and total photoyield spectrum. The roles of the screening by conduction electrons and the sd hybridization are emphasized.
Astronomy & Astrophysics, 2005
We study the effects of using a4d pseudo-orbital on the collision strengths for electron impact excitations of forbidden transitions in Ni computed in the close coupling approximation. It is found that the resonance structures of the collision strengths are quite sensitive to the way the pseudo-orbital is created. Further, the close coupling expansion with a single4d orbital does not converge, resulting in a poor representation of (N + 1)-electrons auto-ionizing states. Much greater expansions are needed to properly represent resonance structures in electron impact excitation calculations, resulting in variations of up to factors of two, with respect to previous computations, in the Maxwellian averaged excitation rate coefficients.
Chemical E'hysics 58 (1981) 409421 North-Holland Publishiig Company OF NICKELOCENE
In this paper we report the results of an experimental study of collision-free molecular multiphoton dissociation (PJPD) and molecular multiphoton ionization (&@I) of nickelocene @KC loH,o), induced by the light of a tunable dye laser in the wavelength region 3750-5200 A. The spectral dependence of the ion signal reveals-a multitude of narrow (fwhm from CO.5 cm-' to 1.5 cm-' _) Intense peaks superimposed on a very weak background (relative amplitude ratio for peakslback-ground ~10~). The sharp resonances in the icn sig~at are attributed, on the basis of spectroscopic anzdysis, to two-photon resonant three-photon ionization of Ni(I) and to one-photon resonant three-photon ionization of Ni(I), the Ni(I) being produced by MPD of nicketocene. The ion signal in the spectral rarge 3750-3950 A reveals enhanced continuous background due to MPI of nickelocene. This ion signal spectra, together with studies of the intensity dependence of the,overall (nickelocene hlPD)-(Ni(1) MPPI) processes, as well as the (nickelocene molecular MPI) reaction, reveal four reactive processes. (a) Two-photon molecular MPI for hw > 3.10 eV photons. (b) Three-photon molecular hIpI forfiw = 3.10-2.10 eV. (c) Twephoton MPD at hw > 2.86 eV. (d) Three-photon MPD for Aw = 2.8-1.9 eV. The overall Cissociation enerm of nickelocene (Nicpa) to give Ni f 2cp was determined to be 5.76 t 0.60 eV and the nvo-photon ionization potential of this molecule is 6.29 + 0.015 eV. Our results provide dynamic evidence concerning a simultaneous " 'explosive " photodissxiation mechanism of Nicpz by process (c) and for the dominating role of the dissociative channel, characterized by a branching ratio of 250 in favor of predissociation over autoionization, for process (c) at 6.3-6.6 eV. The MPD processes (c) and (d) are expected to exhibit intramolecular erosion of phase coherence effects. Processes (c) and (d) are of high efficiency ~0.01 ions/molecule at saturation exhibited at laser power of =108 tV cm " .
The Journal of Physical Chemistry A, 2005
A dispersed fluorescence investigation of the low-lying electronic states of NiCu has allowed the observation of four out of the five states that derive from the 3d Ni 9 3d Cu 10 σ 2 manifold. Vibrational levels of the ground X 2 ∆ 5/2 state corresponding to V) 0-11 are observed and are fit to provide ω e) 275.93 (1.06 cm-1 and ω e x e) 1.44 (0.11 cm-1. The V) 0 levels of the higher lying states deriving from the 3d Ni 9 3d Cu 10 σ 2 manifold are located at 912, 1466, and 1734 cm-1 , and these states are assigned to Ω values of 3 / 2 , 1 / 2 , and 3 / 2 , respectively. The last of these assignments is based on selection rules and is unequivocal; the first two are based on a comparison to ab initio and ligand field calculations and could conceivably be in error. It is also possible that the V) 0 level of the state found at 912 cm-1 is not observed, so that T 0 for the lowest excited state actually lies near 658 cm-1. These results are modeled using a matrix Hamiltonian based on the existence of a ground manifold of states deriving from the 3d 9 configuration on nickel. This matrix Hamiltonian is also applied to the spectroscopically well-known molecules AlNi, NiH, NiCl, and NiF. The term energies of the 2 Σ + , 2 Π, and 2 ∆ states of these molecules, which all derive from a 3d 9 configuration on the nickel atom, display a clear and understandable trend as a function of the electronegativity of the ligands.