Term isotope shift of high lying odd and even energy levels of Nd II

The isotope shifts of the odd and even parity energy levels of singly-ionised neodymium (Nd II) have been evaluated using the measurements carried out in more than 300 spectral lines of Nd II in the region 3290–5820 Å. Term shift, ΔT (¹⁴⁴Nd-¹⁵⁰Nd), is being reported for 23 low even and 15 high lying even parity levels of Nd II. ΔT for a level of 4f ³6s6p configuration and 8 even levels between 36892 and 43212 cm^-1 are being reported for the first time. ΔT values of 151 high lying odd parity levels are being reported and compared with some of the available earlier reported values. ΔT values of 47 odd parity levels are being reported for the first time, most of which are based on our isotope shift studies in UV region. The electronic configuration assignments to energy levels of Nd II by earlier workers are discussed on the basis of present ΔT values. Electronic configurations to some of the unclassified high lying odd levels have been suggested; the levels with ΔT (144–150) between 300mK and 380mK are assigned to 4f ³5d6s configuration whereas a level with ΔT value of 60mK to 4f46p configuration.     

Isotope shifts and electronic configurations of some of the energy levels of the neutral gadolinium atom

Isotope shift ΔT (156–160) have been evaluated for 52 odd and 90 even energy levels of the neutral gadolinium atom from the measurements carried out on 166 lines of the first spectrum in the region 4535–4975 Å on a photoelectric recording Fabry-Perot Spectrometer and enriched samples of ¹⁵⁶Gd and ¹⁶⁰Gd. Earlier studies provide data for just two lines in this region. Assignment of electronic configurations to some of the energy levels have been either confirmed or revised; some unassigned levels have been assigned probable configurations. The present study provides, for the first time, isotope shift of the two levels of 4f⁷6s²7 s configuration of Gd I.     

Reevaluation of term isotope shifts of low even levels of 4f86s2 configuration and high odd-parity levels of neutral gadolinium atoms

Isotope shift ΔT(¹⁵⁶Gd–¹⁶⁰Gd) of the even-parity energy levels of 4f⁸6s² and 4f⁷6s²6p configurations of neutral gadolinium atoms (Gd I) have been reevaluated using the level isotope shift (ΔT) of two odd-parity levels reported recently. Earlier the isotope shifts of these even-parity energy levels were evaluated using empirical relation. Our extensive isotope shift data has been used for the reevaluation of ΔT values of these low even-parity energy levels which have been utilised for revision of the ΔT values of high-lying odd-parity energy levels of Gd I.     

Isotope shifts in energy levels of the neutral neodymium atom

Isotope shift ΔT(142–144) have been evaluated for 281 odd and 110 even levels of the neutral neodymium atom from the isotope shift measurements made in the classified lines of Nd I spectra covering the region 3930–6510 Å. These investigations were carried out on a recording Fabry—Perot spectrometer using enriched isotopes excited in liquid-air cooled hollow cathodes. Electronic configurations of the energy levels have been discussed and probable configurations assigned to many odd and even levels. Most of the high even levels could be assigned to 4f³5d²6p configuration.     

Isotope shift studies in the spectra of Gadolinium in UV region and term shifts of high even levels of Gd I

Isotope shift Δσ(¹⁵⁶Gd?¹⁶⁰Gd) is reported in 70 spectral lines of neutral gadolinium atom (Gd I) in the 3290- 3920 Å region providing isotope shift data in UV lines of Gd I spectrum for the first time. The measurements were carried out on a photoelectric recording Fabry-Perot Spectrometer using highly enriched isotopic samples of gadolinium. Term isotope shifts ΔT(¹⁵⁶Gd?¹⁶⁰Gd) have been evaluated for 48 high lying even parity energy levels of Gd I using this data; new ΔT values have been obtained for 24 levels. Electronic configurations 4f⁷5d6s6p, 4ff⁷5df²6p and 4f⁸5d6s assigned earlier to these even levels have been either confirmed or configuration mixing pointed out in some of these levels. Probable assignment of 4f⁸5d6s configuration to 8 even levels between 32 930 and 35 500 cm^-1 have been confirmed.     

Electronic configurations and isotope shifts of the energy levels of the neutral dysprosium atom

Electronic configurations of the energy levels of the neutral dysprosium atom have been suggested on the basis of isotope shift studies carried out in the first spectrum of dysprosium using highly enriched isotopes excited in liquid-air-cooled hollow cathode lamps and a photoelectric recording Fabry-Perot spectrometer. Isotope shift Δ T(164-160) have been evaluated for 85 even and 82 odd energy levels. The configurations 4f⁹d6s6p, 4f⁹6p6s² and 4f¹⁰6s6d along with two new configurations 4f⁹5d²6p and 4f¹⁰6p² have been assigned to even levels whereas the configurations 4f⁹5d²6s, 4f¹⁰6s6p and 4f¹⁰5d6p have been assigned to some odd energy levels of the neutral dysprosium atom.     

Isotope shifts in the energy levels of the singly ionized neodymium atom

Isotope shifts ΔT (142–144) have been evaluated for odd and even energy levels of the singly ionised neodymium atom from the measurements carried out in 168 spectral lines in the 3930–5820 Å region, employing a recording Fabry-Perot spectrometer and highly enriched isotopes excited in liquid-air cooled hollow cathodes. The electronic configurations 4f³5d6s, 4f³5d6p and 4f⁴6p could be assigned to some of the energy levels on the basis of the present study.     

Isotope shift studies in the UV spectrum of singly ionised gadolinium

Isotope shift Δσ(¹⁵⁶Gd-¹⁶⁰Gd) are reported for 33 spectral lines of singly ionised gadolinium (Gd II) in the 3315–3930 Å region, making use of a photoelectric recording Fabry-Perot spectrometer and highly enriched isotopic samples of ¹⁵⁶Gd and ¹⁶⁰Gd Isotope shift values for these lines have not been reported earlier. Using this data, term isotope shift ΔT(¹⁵⁶Gd-¹⁶⁰Gd) have been evaluated for the even and odd parity energy levels involved in these transitions. We report here ΔT values of only 10 odd parity energy levels lying above 35 000 cm⁻¹, which have been evaluated for the first time. Configuration assignments of six of these levels to 4f⁸6p have been confirmed and probable configurations suggested for four unassigned levels.     

Crossed-second-order effects in the isotope shift for170–166Er and168–166Er in the configuration 4f 12 6s 2

High resolution interference and intermodulated optogalvanic saturation spectroscopy has been applied for isotope shift (IS) studies in the ground-configuration 4f ¹² 6s ² of ErI. For the isotope pairs^170–166Er and^168–166Er the results confirm a strongJ- and term dependence of the IS caused through crossed-second-order (CSO) effects. We performed a parametric analysis to evaluate the CSO-parametersz _4f for the interpretation of theJ-dependence andT(³ H),T(³ F),T(¹ G) to describe the term dependence. The following parameter values (in MHz) were determined, for^170–166Er:z _4f =40.1(0.6),T(³ F)=?153(5),T(³ H)=?220(6), andT(¹ G)=?79(4); for^168–166Er:z _4f =20.1(0.7),T(³ F)=?77(6),T(³ H)=?111(7), andT(¹ G) =?43(5). The normalization of these parameters with the corresponding nuclear parameters λ for both isotope pairs leads to almost identical parameter values indicating a dominant influence of the field shift effect in second-order for thez _4f parameter and in third-order for the parametersT(³ F),T(³ H), andT(¹ G).     

Isotope shifts in spectral lines of Yb+ in 322-615nm region and term shifts of odd and even parity energy levels of Yb II

Isotope shift Δσ(¹⁷²Yb - ¹⁷⁶Yb) has been measured in 79 classified lines of Yb II in the region 3225-6155 Å. Earlier studies provide isotope shift data in just six lines of Yb II. Term isotope shift ΔT (¹⁷²Yb-¹⁷⁶Yb) have been evaluated for 38 even and 30 odd parity levels of Yb II, using the present isotope shift data. The ΔT values have been discussed and correlated with the purity of the configuration assigned to an energy level, which enabled to check the reported eigenvector percentages of different configurations for some of the levels of Yb II. ΔT values of different levels resulting from J_IL_II couplings are also discussed.     

Isotope shifts in odd and even energy levels of the neutral and singly ionised gadolinium atom

Isotope shift studies in the gadolinium spectra have been extended in the region 4140–4535 Å. Isotope shift Δσ(156–160) have been measured in 315 lines of the neutral and singly ionised galolinium atom using a recording Fabry—Perot Spectrometer and gadolinium samples enriched in ¹⁵⁶Gd and ¹⁶⁰Gd isotopes. Some of the Gd I lines studied involve transitions from newly identified high odd levels of 4f⁸6s 6p, 4f⁷5d 6s 7s and 4f⁷5d³ configurations to low even levels of 4f⁸6s² and 4f⁷6s²6p configurations. Electronic configurations of the energy levels have been discussed on the basis of observed isotope shifts. In some cases assigned configurations have been revised and probable configurations have been suggested.     

Isotope shifts and electronic configurations of the odd parity energy levels of singly ionised samarium

Isotope shift ΔT (148–154) has been evaluated for twelve low-lying even and 89 odd parity levels of singly ionised samarium (Sm II) from the isotope shift (IS) studies in 182 spectral lines of Sm II in the 3890–4525 Å region. These studies were carried out on a recording Fabry-Perot spectrometer using eriched isotopes¹⁴⁸Sm (96%) and¹⁵⁴Sm (98%) excited in liquid nitrogen-cooled hollow-cathodes. Earlier data on isotope shifts are available for only eight lines in this region. It has been found that for a few spectral lines there are errors both in magnitudes and signs of isotope shifts, reported earlier. Most of the 89 odd parity levels of Sm II, for which ΔT values have been evaluated presently, have in literature either no electronic configuration assignments or only tentative assignments. We have suggested the leading configuration for most of these odd levels of Sm II on the basis of ΔT values evaluated in the present studies.     

Cross sections for fast-neutron interaction with erbium isotopes

Cross-sections for (n,2n), (n,p), (n,α), and (n,d*) (The expression (n,d*) cross section used in this work includes a sum of (n, d), (n, np) and (n, pn) cross sections) reactions have been measured on erbium isotopes at the neutron energies from 13.5 to 14.8 MeV using the activation technique in combination with high-resolution gamma-ray spectroscopy. Data are reported for the following reactions: ¹⁶²Er(n,2n)¹⁶¹Er, ¹⁶⁴Er(n,2n)¹⁶³Er, ¹⁶⁸Er(n,α)^165mDy, ¹⁶⁶Er(n,p)^166gHo, ¹⁷⁰Er(n,α)¹⁶⁷Dy, ¹⁶⁸Er(n,p)^168m+gHo, ¹⁷⁰Er(n,p)^170gHo, and ¹⁷⁰Er(n,d*)¹⁶⁹Ho. The cross sections were discussed and compared with experimental data found in the literature, and with the comprehensive evaluation data in ENDF/B-VII.0 and l JEFF-3.1/A libraries.     

Location of energy barriers. VI. The dynamics of endothermic reactions,ab + c

A systematic 3D classical-trajectory study has been made of the effect of reagent energy distribution and mass combination on the dynamics of endothermic reaction. The potential-energy hypersurface was endothermic by 35.7 kcal mole^?1. Reagent translation, T′, and vibration, V′, was varied in the range up to T′ + V′ = 90 kcal mole^?. Among the principal findings for the equal-mass case were the following. (i) There is an orders-of-magnitude increase in reaction cross section when energy is transferred from T′ to V′, until an optimal distribution over T′ and V′ is achieved at V′ ?, T′. There is a qualitative difference between the forms of the reactive cross section dependences S(T′) V′ and S(V′)_T′. (ii) The greater efficacy of V′ than T′ in promoting endothermic reaction is marked even at total reagent energies ≈ 3 x the endothermic barrier height. (iii) The total reactive cross section for endothermic reaction increases to large values (≈ gas kinetic) as V′ increased to several times the barrier height. (iv) Reagent energy in excess of that required to cross the endothermic barrier is subject to the same “adiabatic” transformation into product energy as was previously observed for exothermic reactions: ΔT′ → ΔT + ΔR (where R is enhanced product rotational energy), and ΔV′ → ΔV. This is explained in terms of induced repulsive energy release in the former case, and induced attractive energy release in the latter. (v) The molecular product is backwards or sideways scattered. Enhanced V′ at constant T′ diminishes product repulsion, giving rise to more-forward scattering. (vi) These findings remain qualitatively unchanged when extreme mass combinations H H + L and L H + H (L = 1 amu, H = 80 amu) are substituted for the equal-mass combination, L L + L. Effects ascribable to a “late” barrier are accentuated for HH + L. and diminished for L H + H. (vii) The total reactive cross section at a given reagent energy increases in the sequence H H + L, L L + L, L H + H, for simple kinematic reasons. (viii) The dynamics on this endothermic potential-energy surface resemble, in all the points listed above, the dynamics on a thermoneutral surface which has its barrier crest in the coordinate of separation (surface II of part I of this series).     

Simultaneous determination of the activation energy and the reaction kinetic model from the analysis of a single curve obtained by a novel method

It has been demonstrated that a single plot of the values of Δlnα^1/2/Δln(1-α) (taken from a single α?T curve obtained under a controlled linear increase of the reaction rate) as a function of the corresponding values of Δ(1/T)/Δln(1?α) permits the simultaneous determination of both the activation energy and the kinetic model in accordance with a solid state reaction.     

Isotope shift studies in the first spectrum of ytterbium

Isotope shift △σ (172–176) have been measured in 172 lines of the first spectrum of ytterbium in the region 3900–6500 Å employing a recording Fabry—Perot spectrometer and highly enriched isotopes excited in liquid-air-cooled hollow cathodes. Out of the 172 lines studied, energy level classifications are available for 167 of them. Isotope shift △T (172–176) of 62 even and 59 odd energy levels of Yb I have been evaluated and their electronic configurations discussed.     

High-energy collisional activation studied via angle-resolved translational energy spectra of survivor ions

Angle-resolved translational energy spectroscopy has been applied to Cs₄I ₊ ³ ions that survived 8 keV collisions with a range of collision gas targets, including inert gases and deuterium. The experimental data comprise values of the translational energy loss ΔT_R as a function of the (laboratory-frame) scattering angle θ _R for each collision gas under conditions such that single-collision events dominated the scattering. The values of ΔT_R increase with θ _R, in accordance with very general expectations. However for any value of θ _R, the values of ΔT_R for helium and deuterium as targets were almost indistinguishable from one another but were at least five to six times larger than those for neon and all other collision gases. These data have been shown to be consistent with theoretical considerations based upon conservation of energy and linear momentum. Theoretical approaches include the simple “elasticlimit” model, which makes no mechanistic assumptions, and a particular “binary-model” theory, which excludes electronic excitation as a possibility. Both theories are consistent with the experimental data and interpret the surprisingly large values of ΔT_R for low-mass targets in terms of large recoil energies of the target required to ensure conservation of momentum. The most likely alternative candidate as sink for ΔT_R is internal excitation of the target, but this possibility was excluded in the present work by choosing ΔT_R values less than the lowest excitation energies of the inert gas targets. Moreover, such an interpretation cannot explain the similar results obtained using helium and deuterium, which were markedly different from those obtained for all other collision gases.     

Laser spectroscopic investigation of isotope shifts in Nd II lines

The isotope shift of 11 optical transitions in Nd II in the spectral range 420–450 nm have been recorded (in all cases but one for all pairs of even Nd isotopes). For all observed transitions the values of the field shifts, the specific mass shifts and Δ∣ψ(0)∣² have been evaluated. Using our new data, combined with data reported in earlier papers, term isotope shifts for all pairs of even Nd isotopes have been determined for 27 energy levels and for the configurations: 4f⁴6s, 4f⁴5d, 4f³5d6s and 4f⁴6p as well. It is shown that configuration assignment of a level on the basis of term shift values only is in some cases not satisfactory (as e.g. of the level at 22,696 cm⁻¹) and obviously additional information is required.     

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.     

Isotope shift studies in the second spectrum of neodymium in UV region

Isotope shift (IS) Δσ (142–150) have been measured in 92 spectral lines of Nd⁺ in the region 3290–3955 Å, employing recording Fabry-Perot spectrometer and highly enriched isotopic samples excited in a liquid-nitrogen cooled hollow cathode. Earlier IS measurement in UV region of Nd II spectrum is available for only a few lines, New classification has been made for several of the spectral lines studied presently. We have also revised the earlier suggested classification for some of the Nd II lines on the basis of observed isotope shifts. The transitions presently studied mostly involve high lying odd parity energy levels above 30,000 cm^?1 having neither electronic configuration assignment nor term isotope shifts (ΔT) evaluated. The present study would thus enable to evaluate ΔT values of some of these high lying odd levels, which should be helpful in suggesting possible electronic configurations.