Excitation of the Yb II transitions terminating on the low-lying odd levels

Excitation of the transitions from the even levels of a singly charged ytterbium ion that terminate on the low-lying odd levels 4f ¹³(² F°)6s ^{2 2} F°, 4f ¹⁴(¹ S)6p ² P°, and 4f ¹³(² F°_7/2)5d6p(³ D)³[3/2]° is experimentally studied by measuring 51 excitation cross sections at an electron energy of 50 eV, and 16 optical excitation functions are determined within the electron energy range 0–200 eV. The largest magnitudes of the measured cross sections exceed 3 × 10^?17 cm².     

Time constants of radiative transitions from the 5<Emphasis Type="Italic">d</Emphasis>[3/2]<Subscript>1</Subscript> level of a xenon atom

Integral yields of spontaneous emission at wavelengths of 1.73, 2.03, and 2.65 μm have been measured upon excitation of pure xenon by a pulsed electron beam. These yields have been analyzed and experimental data have been obtained on time constants of radiative transitions 5d[3/2]₁ → 6p[5/2]₂, 5d[3/2]₁ → 6p[3/2]₁, and 5d[3/2]₁ → 6p[1/2]₀ of XeI, which appeared to be equal to (2300 ± 400) × 10^?9, (300 ± 40) × 10^?9, and (1300 ± 200) × 10^?9 s, respectively. It is shown that the experimental data are in a qualitative agreement with the results of computational and theoretical investigations. The results of averaging the experimental and calculated data are proposed for use as recommended values of the corresponding constants.     

Anregungsfunktionen für die (d,p)-, (d,n)-und (d,2n)-Reaktionen an Ce142 bis 11,8 MeV

Total cross sections and excitation functions up to 11·8 MeV have been measured for the Ce¹⁴²(d,p), -(d,n) and -(d, 2n) reactions by the activation method. The cross sections found forE _d=11·8 MeV are 187mb, 54 mb and 535 mb, respectively. By comparing these results with cross sections calculated from the statistical theory of nuclear reactions it can be shown that the (d,p)-reaction and nearly the whole (d,n) -reaction proceed by stripping mechanism.     

Many-electron character of Rydberg series converging to the ionization thresholds of the 4<Emphasis Type="Italic">p</Emphasis><Superscript>4</Superscript>5<Emphasis Type="Italic">s</Emphasis> states of KrII

The photoionization cross sections of the 4p shell and the 4s main level and 4p ⁴(³ P) 5s ⁴ P _{5/2, 3/2} satellite subvalence levels of KrII have been calculated in the 4s-near-threshold range of excitation energies from 28.48 to 28.70 eV. The calculation takes into account the core relaxation by the methods of the theory of non-orthogonal orbitals, the interaction between resonant states through autoionization channels by solving the complex secular equation, and the interaction between the channels of the continuous spectrum in all orders of the perturbation theory by the K-matrix method. Good quantitative agreement between the energy-integrated theoretical and experimental photoionization cross sections for the satellite levels has been obtained for the first time. It is shown that only simultaneous consideration of the above-mentioned effects leads to such agreement. The resonant structure of the photoionization cross sections in this excitation energy range is related to the autoionization decay of the 4p ⁴5s(⁴ P _1/2)np and 4p ⁴5s(² P _3/2)np Rydberg series. The specificity of this process is that both series manifest themselves not independently but owing to their strong electrostatic interaction with the prominent 4p ⁴(¹ D)5s ² D _5/2 6p _3/2 resonance, which lies in this excitation energy range.     

Theoretical study of photoionization of the isoelectronic sequence Rb<Superscript>+</Superscript>, Sr<Superscript>2+</Superscript>, and Y<Superscript>3+</Superscript>

The photoionization cross sections for the 4p shell of ions of the Kr isoelectronic sequence Rb⁺, Sr²⁺, and Y³⁺ are calculated. The configuration interaction theory and the perturbation theory are used to describe the many-electron effects. The relativistic effects are taken into account in the Pauli-Fock approximation. The calculated resonance structure of photoionization cross sections for the 4p shell in the region below the 4s threshold associated with the autoionization of the 4s-np singly excited states and the 4p4p-nln′l′ doubly excited states reproduces the results of recent measurements of total photoabsorption cross sections for the Rb⁺, Sr²⁺, and Y³⁺ ions. It is found that, as the nuclear charge in the isoelectronic sequence increases, the ratio between the direct and correlation parts of amplitudes of the 4s-(n/?)p transition changes and, as the consequence, the minimum of the photoionization cross section of the 4s shell shifts from the continuous spectrum to the region of states of discrete spectrum. This accounts for the strong changes in the shape of the 4s-np resonances in the photoionization cross sections for the 4p shell of Rb⁺, Sr²⁺, and Y³⁺, as well as the distinction between the shapes of the 4s-6p _1/2 mirror resonance in the partial 4p _1/2 and 4p _3/2 photoionization cross sections for the Y³⁺ ion which do not suppress each other in the total photoionization cross section, as is the case for similar resonances in Rb⁺ and Sr²⁺.     

Cross sections of the photoneutron reaction for <Superscript>141</Superscript>Pr and <Superscript>186</Superscript>W nuclei,estimated from physical criteria of data reliability

Using objective physical criteria for data reliability, cross sections of partial photoneutron reactions (γ, 1n), (γ, 2n) and (γ, 3n) that are free of the shortcomings of neutron multiplicity sorting methods used on beams of quasimonoenergetic annihilation photons are obtained for ¹⁴¹Pr and ¹⁸⁶W nuclei. Evaluation is performed using the experimental–theoretical method (ETM), based on the experimental cross section of neutron yield reaction σ^exp(γ, xn) = σ^exp(γ, 1n) + 2 σ^exp(γ, 2ⁿ) + 3 σexp(γ, 3n) + … and ratios F _i ^theor= σ^theor(γ, in)/σ^theor(γ, xn) calculated within the combined model (CM) of photonuclear reactions, which stipulates that σ^eval(γ, in) = F _i ^theor σ^exp(γ, xn). It is found that for ¹⁴¹Pr and ¹⁸⁶W, ratios F ^exp _i do not contradict the data reliability criteria only at energies up to ~21 and ~22 MeV, respectively. At the same time, there are notable discrepancies between F _i ^theor and F ^exp _i, and thus between the evaluated and experimental cross sections of reactions. It is shown that the discrepancies between the evaluated and experimental cross sections are due to the assumed unreliable experimental distribution of neutrons in the channels with multiplicities 1, 2, and 3.     

Reliability of the data on the cross sections of the partial photoneutron reaction for <Superscript>63,65</Superscript>Cu and <Superscript>80</Superscript>Se nuclei

The cross sections of partial photoneutron reactions are evaluated for the ^63,65Cu and ⁸⁰Se isotopes. The cross sections are free of systematic uncertainties from shortcomings of the experimental methods for neutron multiplicity sorting based on measurements of neutron energy used in experiments with quasimonoenergetic annihilation photon beams. An experimental-theoretical method is used to evaluate cross sections σ^eval(γ, in)= F_i^theor σ^exp(γ, xn), where ratios F_i^theor = σ^theor(γ, in)/σ^theor(γ, xn) = σ^theor(γ, in)/σ^theor[(γ, 1n) + 2(γ, 2n) + …] are calculated using a combined model of photonuclear reactions, and σ^exp(γ, xn) is the experimental cross section of the neutron yield reaction free from neutron multiplicity sorting problems. The cross sections are evaluated for reactions (γ, 1n) and (γ, 2n) for the ^63,65Cu and ⁸⁰Se isotopes, and for the total photoneutron reaction σ(γ, Sn) = σ[(γ, 1n) + (γ, 2n) + …]. It is shown that noticeable deviations of the experimental cross sections from the evaluated values result from the unreliable sorting of neutrons between the channels with multiplicities 1 and 2.     

Bestimmung des Kompoundkern- und Stripping-Anteils der (d,p)- und (d,n)-Reaktionen an Zr94 und Zr96

An experiment has been accomplished which gives information on the reaction mechanism of the (Zr^94,96+d)-reactions. Total cross sections and excitation functions up to 11,8 MeV have been measured for the reactions Zr⁹⁴ (d, p), Zr⁹⁴ (d, n), Zr⁹⁶(d, p), Zr⁹⁶(d, n) and Zr⁹⁶(d, 2n) by the activation method. The results are compared with cross sections calculated according to the statistical theory of nuclear reactions. It is shown that the (d, p) -reactions proceed almost completely by the stripping-mechanism. The (d, n)- and (d, 2n)-excitation functions on the other hand are in good agreement with the predictions of the statistical theory and one can conclude that the compound nucleus mechanism is the dominating process.     

Dissociative Excitation of the Odd Sextet Levels of the Cobalt Atom by Collisions of Electrons with Cobalt Dichloride Molecules

Inelastic collisions of slow electrons with cobalt dichloride molecules, leading to the formation of excited cobalt atoms in odd sextet states, are experimentally studied. At an incident electron energy of 100 eV, thirty six dissociative excitation cross sections are measured for levels belonging to the z⁶D°, z⁶F°, and z⁶G° terms. In the electron energy range of 0–100 eV, ten optical excitation functions are recorded. The full cross sections for the dissociative excitation of the cobalt atom levels and the contribution of cascade transitions to their population are determined. The cross sections for electron–molecule and electron–atom collisions are compared.     

Excitation of a singly charged Sr Ion by e-Sr collisions

Excitation of spectral lines of SrII, including laser lines, is studied experimentally in collisions of slow electrons with strontium atoms. Twenty-one excitation cross sections are measured at an energy of electrons of 30 eV. Five optical excitation functions are recorded at an energy ranging from 0 to 200 eV. Direct-excitation cross sections for the 5p ² P°_{1/2, 3/2} levels and the contribution to their population by cascade transitions are calculated. Excitation cross sections of two laser transitions in the IR spectral region are determined using known branching ratios. The results obtained are compared with data of previous experiments.     

Manifestation of the Coster-Kronig effect in the near-threshold electron-impact excitation of the Cd<Superscript>+</Superscript> ion

The near-threshold portions of the energy dependences of the effective excitation cross sections of the resonance transition 4d¹⁰5p²P_1/2° → 4d¹⁰5s²S_1/2 and the two-electron forbidden transition 4d⁹5s²²D_5/2 → 4d¹⁰5p²P_3/2° in the spectrum of the Cd⁺ ion were investigated by the spectroscopic method in crossed electron and ion beams. In the region of energy splitting of the ²P° and ²D levels, a significant resonance contribution of the autoionizing states of cadmium (decaying during the Coster-Kronig process) to the effective excitation cross sections of the noted transitions was revealed for the first time. It is found that the resonance contribution manifests itself much more strongly for the forbidden transition in comparison with the more intense resonance transition; i.e., the manifestation of the Coster-Kronig effect in the electron excitation of ions depends strongly on the cross section of the direct process. It is ascertained that, during the Coster-Kronig process, the main contribution to the resonance excitation of both the resonance and the two-electron forbidden spectral transitions is from the low-lying terms of the series of autoionizing states 4d¹⁰5p(²P_3/2°)ns, md and 4d⁹(²D_3/2)5s²ns, md, which are in the splitting region of the ²P_{1/2, 3/2}° and ²D_{5/2, 3/2} levels, rather than from the high-lying atomic autoionizing states of cadmium, which are located near the ionization limits (corresponding to the and ²P_3/2° and ²D_3/2 levels).     

Untersuchungen von (d,p)- und (d, α)-Reaktionen an B10 und B11

Investigating reaction mechanisms, angular distributions and cross sections of the reaction B¹⁰(d, p) B¹¹ have been measured in the energy interval from 1,4 to 3,3 MeV of deuteron energy. More detailed measurements than until known have shown, that besides the well known stripping mechanism withl _n =1 contributions of compound nucleus formation are not neglectable. Especially atE _d =2,3 MeV,E _X (C¹²)=27,1 MeV, the effect of a single resonance contributes a great deal to the cross section of the groupsp ₁ andp ₃ . Further angular distributions and yield curves between 1,4 and 3,3 MeV have been measured in the (d, α)-reactions on B¹⁰ and B¹¹, showing quite different behaviour for both target nuclei.     

Physical criteria for the reliability of data on the photodisintegration of the <Superscript>89</Superscript>Y nucleus

Experimental photonuclear reaction cross sections obtained in experiments using quasimonoenergetic annihilation, monoenergetic tagged photons, and bremsstrahlung γ-radiation are analyzed using physical criteria for the reliability of data on the ⁸⁹Y nucleus. It is found that the reliability of data on the cross sections of partial reactions (γ, 1n) and (γ, 2n), obtained by means of photoneutron multiplicity sorting, is highly doubtful. Reliable cross sections of reactions (γ, 1n) and (γ, 2n) are obtained using the experimental–theoretical method (ETM) for evaluating using both experimental cross sections of neutron yield reaction σ^exp(γ, xn) that are free of neutron multiplicity problems, and theoretically calculated F _i ^theor ratios of the cross sections of definite (i) partial reactions to cross section σ^theor(γ, xn). It is shown that the evaluated cross sections differ noticeably from the experimental data.     

Precision measurements of optical excitation functions for the cadmium atom

An experimental setup and a technique for the investigation of excitation of atoms by ultramonoenergetic electrons are described. The optical excitation functions are given for 14 spectral lines of the cadmium atom originating from the n ¹ S ₀, 5¹ P ₁, n ³ S ₁, 5³ P ₁, and n ³ D _j levels. More than 150 specific features are found in the energy dependences of the effective excitation cross sections measured from the excitation threshold to 16 eV. The most pronounced of these features are in good agreement with the fine structure observed previously. The main mechanisms of the initial-level population, namely, the direct transition of an electron from the ground atomic state to the initial level of a spectral line, the population of the initial levels due to the decay of short-lived states of a negative ion, and the cascade population, are separated. In the excitation functions of the lines originating from the n ¹ S ₀ levels, in the energy range from 10.9 to 12.4 eV, we observed for the first time an effect of postcollision interactions of emitted and scattered electrons in the vicinity of the thresholds of four autoionization states of the cadmium atom.     

Rotational properties of the odd-Z transfermium nucleus 255Lr by a particle-number-conserving method in the cranked shell model

Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514]Nilsson state of the odd-Z nucleus ~(255)Lr are studied by the cranked shell model(CSM) with the paring correlations treated by the particle-number-conserving(PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia(J~(1)and J~(2)) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia J~(1) with the experimental ones extracted from different spin assignments, the spin 17/2~-→13/2~- is assigned to the lowest-lying 196.6(5) ke V transition of the 1/2~-[521] band, and 15/2~-→11/2~- to the 189(1) ke V transition of the 7/2~-[514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high- j low-? 1 j_((15)/2)(1/2~-[770]) orbital at the high spin leads to band-crossings at ω≈0.20( ω≈0.25) Me V for the 7/2~-[514] α =-1/2(α = +1/2) band, and at ω≈0.175 Me V for the1/2~-[521] α =-1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.     

Modern status of photonuclear data

The reliability of experimental cross sections obtained for (γ, 1n), (γ, 2n), and (γ, 3n) partial photoneutron reactions using beams of quasimonoenergetic annihilation photons and bremsstrahlung is analyzed by employing data for a large number of medium-heavy and heavy nuclei, including those of ^63,65Cu, ⁸⁰Se, ^90,91,94Zr, ¹¹⁵In, ^112?124Sn, ¹³³Cs, ¹³⁸Ba, ¹⁵⁹Tb, ¹⁸¹Ta, ^186?192Os, ¹⁹⁷Au, ²⁰⁸Pb, and ²⁰⁹Bi. The ratios of the cross sections of definite partial reactions to the cross section of the neutron-yield reaction, F _i = σ(γ, in)/σ(γ, xn), are used as criteria of experimental-data reliability. By definition, positive values of these ratios should not exceed the upper limits of 1.00, 0.50, 0.33,... for i = 1, 2, 3,..., respectively. For many nuclei, unreliable values of the above ratios were found to correlate clearly in various photon-energy regions F _i with physically forbidden negative values of cross sections of partial reactions. On this basis, one can conclude that correspondent experimental data are unreliable. Significant systematic uncertainties of the methods used to determine photoneutron multiplicity are shown to be the main reason for this. New partial-reaction cross sections that satisfy the above data-reliability criteria were evaluated within an experimental–theoretical method [σ ^eval(γ, in) = F _i ^theor (γ, in) × σ ^expt(γ, xn)] by employing the ratios F _i ^theor (γ, in) calculated on the basis of a combined photonuclear-reaction model. It was obtained that cross sections evaluated in this way deviate substantially from the results of many experiments performed via neutron-multiplicity sorting, but, at the same time, agree with the results of alternative activation experiments. Prospects of employing methods that would provide, without recourse to photoneutron-multiplicity sorting, reliable data on cross sections of partial photoneutron reactions are discussed.     

Precision measurements of optical excitation functions for the mercury atom

We describe a computer-based facility for studying the excitation of atoms by ultramonochromatic electrons and give optical excitation functions for the 12 mercury spectral lines that originate from the n ¹ S ₀, n ¹ P ₁, n ¹ D ₂, n ³ S ₁, n ³ P _j , and n ³ D _j levels. We detected about 100 features in the energy dependences measured from the excitation threshold to 15.5 eV. The previously found positions of the features on the energy scale are in good agreement with our results. Most of the resonant features are shown to be mainly attributable to the decay of short-lived states of the negative mercury ion. We detected a postcollision interaction effect in the optical excitation functions of the lines that originate from the n ¹ S ₀ levels at energies of about 11 eV.     

Evaluation of the Integrated Cross Sections of Reactions of Exclusive Pion and Kaon Electroproduction off Protons in the Resonance Region at Photon Virtualities from 5 to 12 GeV<Superscript>2</Superscript>

The integrated cross sections of the ep → eπ⁺n, ep → eπ⁰p, ep → eK⁺Λ, and ep → eK⁺Σ⁰ reactions are evaluated in the energy range of nucleon resonance excitation at photon virtualities Q² from 5 to 12 GeV². These exclusive channels will be explored at photon virtualities Q² > 5 GeV² for the first time in future experiments with the CLAS12 detector. The cross-section evaluation is based on the extrapolation of exclusive contributions to the inclusive structure functions F₁ and F₂ from a region of Q² < 5 GeV², in which the experimental data are available, to the region of higher Q². This evaluation of cross sections is of particular importance in the development of the program of experiments with the CLAS12 detector for studying the structure of the ground and excited nucleon states, which may reveal the dynamics of strong interactions in the nonperturbative regime.     

Isotope shifts of the ground state of neon: Refining the measurement results

Abstract—It has been revealed that the published results of measurements of the isotope shift of the ground state of even neon isotopes contain systematic errors. The errors are caused by the use of erroneous data regarding the absolute values of specific mass shifts of excited states and by the measurement errors of the isotope shifts themselves for transitions to the ground state. The isotope shift of the 2p⁵4s[3/2]₁ → 2p⁶(¹S₀) transition has been measured to be 2305 ± 20 MHz, the absolute specific mass shift of the 3p[3/2]₂: (2_р9) level has been determined to be 647 ± 10 MHz, and the isotope shift of the ground state has been found to be–3156 ± 30 MHz.