Selective Cross Sections Research Articles

State selective classical electron capture cross sections in Be4+ \u2009+\u2009H(1s) collisions with mimicking quantum effect

We present state-selective electron capture cross sections in collision between Be4+ and ground state hydrogen atom. The n- and nl-selective electron capture cross sections are calculated by a three-body classical trajectory Monte Carlo method (CTMC) and by a classical simulation schema mimicking quantum features of the collision system. The quantum behavior is taken into account with the correction term in the Hamiltonian as was proposed by Kirschbaum and Wilets (Phys Rev A 21:834, 1980). Calculations are carried out in the projectile energy range of 1–1000 keV/amu. We found that our model for Be4+ + H(1s) system remarkably improves the obtained state-selective electron capture cross sections, especially at lower projectile energies. Our results are very close and are in good agreement with the previously obtained quantum–mechanical results. Moreover, our model with simplicity can time efficiently carry out simulations where maybe the quantum mechanical ones become complicated, therefore, our model should be an alternative way to calculate accurate cross sections and maybe can replace the quantum–mechanical methods.

Line intensities for x-ray emission in Mg12+ collisions with H and He atoms

State selective charge transfer cross sections are calculated in Mg12+ collisions with H and He atoms at incident energies of 1.0, 3.0, and 5.0 keV amu−1 using a time-dependent lattice method. Total capture cross sections using the time-dependent lattice method are found to be larger than those previously calculated using the Landau–Zener method. Lyman line ratios are calculated using the time-dependent lattice capture cross sections and standard radiative transitions for both the H and He atoms. Lyman line probabilities are presented for both H and He. The strongest probability for both H and He is the Lyman α emission, but relatively strong probabilities for He at an incident energy of 1.0 keV amu−1 are found for Lyman β, γ, δ, and ϵ emission.

Сечения образования ионов He-=SUP=-+-=/SUP=- в различных электронных состояниях при столкновениях ионов He-=SUP=-2+-=/SUP=- с атомами водорода

Using collision spectroscopy based on precision measurements of the kinetic energy of projectile ions that capture an electron, we measured the state selective electron capture cross sections of formation of He^+(n) ions at collision 3^He^{2 +} ions with an energy of E = 1.4-10 keV/a.m.u. with hydrogen atoms. The atomic hydrogen target with a degree of dissociation 78% at a temperature of tungsten dissociation cell 2180K has been made.

Hydrokinetic energy harnessing by spring-mounted oscillators in FIM with different cross sections: From triangle to circle

Flow-Induced Motion (FIM) phenomena of spring-mounted oscillators were numerically investigated with 2-dimensional simulations to examine the effects of cross section on hydrokinetic energy harnessing. In the simulations, the test flow speed increases from 0.2 m/s to 3.0 m/s (1.61×104 <Re (Reynolds number) < 2.42×105). Six selective cross sections (i.e. triangle, square, hexagon, octagon, 24-sided polygon, and circle) are applied in this study. Results suggest that in the Vortex-Induced Vibration (VIV) region, the response of circular cylinder is the strongest; the maximum amplitude (0.078 m) and maximum converted power (4.6W) are achieved at Re = 4.6×104. Meanwhile, the maximum energy conversion efficiency (34.5%) is also obtained in the VIV region. In the galloping region, decreasing the number of sides of cross section will enhance the FIM responses. More specifically, the amplitude and converted power of the triangular prism are the highest. However, the energy conversion efficiency in the galloping region is significantly lower than that in the VIV region, although the maximum converted power is always obtained at the highest flow speed in the galloping region. Besides, for the smooth circular cylinder, when Re > 9.6 × 104, the amplitude approaches zero, which means the frequency lock-in phenomenon disappears and the response no longer belongs to VIV or galloping.

Line ratios for x-ray emission in O8+ collisions with H and He atoms

A time-dependent lattice method is used to calculate state selective charge transfer cross sections in O8+ collisions with H and He atoms at incident energies of 1.00, 4.00, and 8.18 keV amu−1. Using standard radiative transitions, Lyman (β/α), Lyman (γ/α), and Lyman (δ/α) line ratios are calculated using time-dependent lattice capture cross sections for both H and He. The line ratios for He are found to be in good agreement with direct experimental measurements at 3.11 keV amu−1.

State-selective electron capture in 30- and 100-keVHe++Hecollisions

A combined experimental and theoretical study on single capture in 30- and 100-keV ${\mathrm{He}}^{+}$ on He collisions was performed. By using a reaction microscope, we obtained the state selective cross sections and the angular-differential cross sections. It was found that the experimental state-selective cross sections were in good agreement with the dynamic screening classical trajectory Monte Carlo calculation for 100-keV ${\mathrm{He}}^{+}$ incident. The comparisons with various versions of such calculations reveal the roles played by different electron-electron correlation effects. Moreover, a prominent oscillatory structure was observed in the angular-differential cross sections for both projectile energies. With the single capture probability distribution obtained from the classical trajectory Monte Carlo calculation, the oscillation structures can be well explained by atomic-size Fraunhofer-type diffraction.

Geordnete Spontaneität: Lyrische Subjektivität bei Achim von Arnim by Jan Oliver Jost-Fritz

Reviewed by: Geordnete Spontaneität: Lyrische Subjektivität bei Achim von Arnim by Jan Oliver Jost-Fritz Christian P. Weber Jan Oliver Jost-Fritz, Geordnete Spontaneität: Lyrische Subjektivität bei Achim von Arnim. Heidelberg: Universitätsverlag Winter, 2014. 267 pp. This dissertation contributes to an emerging trend in literary studies that dismisses the doctrine of an aesthetics of autonomy, which aims to interpret individual poems as unique lyrical events, in favor of a more holistic phenomenological approach that considers lyric poetry capable of revealing emotive and cognitive processes, metapoetic reflections, and important general insights into our human condition. Jan Oliver Jost-Fritz uses Achim von Arnim’s poetry to make his case for such an approach. Although Achim von Arnim has certainly not gained the reputation of a leading Romantic poet—his critics found his poems lacking in emotional depth, beauty, and consistency of quality—Jost-Fritz considers Arnim’s prolific, yet often raw and unfinished, lyric productions exemplary for the period’s epistemological transformations and semantic crises. His attempt at a more positive reassessment is based on the definition of the lyrical genre “als Medium” that operates at the intersections between “Natur und Geist, Leib und Seele” (9) and also balances out the spontaneity of ingenious creativity in the laborious process of articulating lyrical events in poetic language and form. Poetry reflects the experiences of the inner life with the outer world and the poet’s engagement with the principal discourses of the politically, philosophically, and scientifically revolutionary era at the turn of the nineteenth century. The totality of emerging poems thus constitutes a subjective poetic vision of reality that manifests and reflects the poet’s individuality. With this premise, Jost-Fritz contradicts the two main previous studies on the same topic by Ulfert Ricklefs and Thomas Sternberg, who detect a lack of subjectivity as the trademark of Arnim’s poems and present him as a pioneer of modern poetry. To collect the traces of subjectivity that he asserts, Jost-Fritz analyzes the form as well as the poetological and anthropological content of a selective cross section of Arnim’s lyric oeuvre. Chapter 1 deals primarily with two earlier poems (“Wenig Töne sind verliehen” and “Ein Herzog sinnt beim Wasserfall”) that pro-grammatically reflect on the problematic relationship between subjective sensitivity and linguistic objectification at the core of Arnim’s poetic persona. Chapter 2 shows in a detailed analysis of two versions of the same poem, entitled “Waldgeschrey” (1808) and “Stolze Einsamkeit” (1813), how poetic subjectivity aims to consolidate its precarious identity in a series of self-reflections resulting in an ever more religiously charged subliminal experience that, according to Jost-Fritz, indicates the dawn of a new phase in Arnim’s lyric oeuvre. The longer romances Die Rose and Der Rheinfall, the subject matter of the following chapter, display the poet’s quest to further explore the depths of the human psyche and the richness of individual experience within cultural history and society. At the end of both poems, the lyric subject realizes the limits of his purely immanent soul- and world-wrenching and articulates his longing for salvation from this earth-bound existence. Chapter 4 covers no fewer than ninety-three sonnets of [End Page 309] the cycle Geschichte des Herrn Sonet, which Jost-Fritz reads as an implicit Bildungsroman. Here, Arnim recapitulates his poetic career and metapoetically reflects the poetic process as a whole, which results, for Jost-Fritz, in a “sentimen-tale Ästhetik” (250). The final chapter, dealing mostly with examples from Arnim’s later poetry, picks up the central theme of poetry as mediating between two different worlds and states of mind/affect by shifting to a cosmic scale with poetic subjectivity “hovering” between heaven and earth, immanence and transcendence. Here, the lyric voice expresses the poet’s thoughts and feelings “durch eine Art erhabener Ironie” (250) that quintessentially captures the tragic reality of the human condition and yet also affirms its potential for freedom by means of poetry and art. This brief summary cannot do justice to the nuanced and subtle readings of the mentioned poems, which are strongest in the chapters that deal with only a few individual poems. In...

Single charge transfer in collisions with H and He atoms

A time-dependent lattice (TDL) method is used to calculate state selective charge transfer cross sections in collisions with H and He atoms. The (nl) capture cross sections for energies of 2.7, 5.2, and 8.3 keV amu−1 are found to be in good agreement with recent atomic-orbital close-coupling (AOCC) calculations for H and somewhat larger than previous AOCC calculations for He. Using standard radiative transition rates, Lyman β/α and γ/α line ratios are calculated using TDL and AOCC capture cross sections for both H and He. The theoretical line ratios for He are found to bracket recent experimental measurements.

Behavior of relative state selective photoionization cross sections of RbBr molecules in the valence region

The photon energy dependence of relative photoionization cross sections in the valence ionization energy region of 5 to 45 eV for 4p and 4s orbitals of Rb and Br ions in RbBr vapors has been investigated. The behavior of state selective cross sections of molecular valence orbitals has been analyzed by comparing the observed 4p to 4s photoelectron intensity branching ratios with atomic state selective photoionization cross sections of Kr, taking into account the mixing between Br 4s(-1) and Rb 4p(-1) molecular states. Using atomic dipole matrix elements to calculate the photoionization intensity of alkali halides has been suggested.

Calculation of ionization and total and partial charge exchange cross sections for collisions of C6+ and N7+ with H

We have performed calculations for collisions between fully stripped ions, C6+ and N7+, and atomic hydrogen, in both its ground and first excited energy levels. We have employed the Classical Trajectory Monte Carlo method to obtain total ionization and charge exchange cross sections and state selective charge exchange cross sections in the 5–500 keV/amu energy range.

State selective photo-recombination cross sections in Be-like C and Al ions

We report results from detailed state selective photo-recombination study along with the doubly excited autoionizing resonances in Be-like C2+ and Al9+ ions. In the present investigation, the primary focus is on detailed energy profiles of the individual photo-recombination cross sections. The calculation was carried out for the excited Rydberg states of type 1s22sns(1Se) which interact with the odd-parity continua up to the C3+ and Al10+ 2p threshold limit. The numerical evaluation has been performed at a fine energy mesh across all the autoionizing Rydberg series of resonances 1s22pns(1P0) converging to Li-like ion 2p threshold. The method of calculation keeps the essential ingredients of the Feshbach projection operator approximation. The photo-ionization cross sections have been evaluated with and without relativistic effects included into the R-matrix numerical procedures, while the allowance for both quantum interference between dielectronic and radiative recombination, and overlapping resonances has been done utilizing results from the earlier R-matrix Floquet calculation. We discuss all these results with respect to the effect of quantum interference term on the energy dependence profile of photo-recombination cross section for studied transitions.

Strong multiple-capture effect in slow Ar17+–Ar collisions: a quantum mechanical analysis

A recent x-ray spectroscopy experiment on Ar17+–Ar collisions at the velocity of 0.53 au provided evidence for strong multiple electron capture (Trassinelli et al 2012 J. Phys. B: At. Mol. Opt. Phys. 45 085202). We have investigated single and multiple captures in the same system by coupling a quantum-mechanical independent electron model calculation for the collision dynamics with a phenomenological Auger model to obtain n selective capture cross sections for n = 2 to n = 10. Using these cross sections and a radiative cascade scheme, we obtained x-ray emission intensities that can be compared with the experimental data. Good agreement is found for the Lyman series from n = 3 to n = 7 if the multiple capture contributions are included, whereas calculations that ignore them are in stark conflict with the measurements.

Electron-impact state-to-state resolved cross sections and rate coefficients for the X(v) → A(v′) excitation in BeH molecules

Electron-impact cross sections are calculated for the v → v′ transitions occurring between the vibrational levels of the two X 2Σ+ and A 2Π electronic states of the BeH molecule. The calculations are performed with the R-matrix method for a purely vertical electronic transition for energies from threshold to 15 eV, and by using a modified version of the Mott and Masssey approximation to extend the calculations to high energies and to vibrational excitations. Rate coefficients are also calculated for the same transitions. The calculated v–v′ selective cross sections and rate coefficients both satisfy distinct scaling relationships, which can be represented in a simple analytic form.

Charge exchange processes involving highly charged ions and targets of interest in astrophysics and fusion plasmas

Renewed interest in charge exchange processes involving highly charged ions arises because of their crucial role in the planned ITER reactor as well as to recent X-ray observations in the astrophysical context. In this work, the classical trajectory Monte Carlo method (CTMC) is used to calculate state selective single charge exchange n-level cross sections and line emission cross sections pertinent to both fields. These are contrasted to recent laboratory data from KVI for the Xe18+ + Na(3s) collision system and NIST/BERLIN-EBIT data for the Ar18+ +Ar system.

Electron transfer and ionization in collisions of He-like ions with Na(3s) and Na(3p)

Single electron transfer and ionization in collisions of He-like ions (N5+, O6+, Ne8+) and Na has been investigated both experimentally and theoretically at energies around the matching velocity of the valence electron (2 to 10 keV/amu). State selective cross sections and scattering angle distributions were obtained using recoil-ion momentum spectroscopy in combination with a magneto-optically cooled Na atom target. A strong dependence of the relative cross sections on the collision energy is observed. The results are compared with Classical-Trajectory Monte Carlo (CTMC) calculations and show an overall very good agreement.

State-selective radiative recombination cross sections of argon ions

The n-, (n,l)- and fine-structure level state-selective radiative recombinations (RR) cross sections of argon ions Ar18+,Ar13+,Ar7+ and Ar+ are obtained with the semi-classical Kramer formula, the relativistic self-consistent field (RSCF) method and the relativistic configuration interaction (RCI) method. It is found that for the highly charged ions with few electrons, the cross sections calculated with these three methods are in good agreement with each other. But as the number of electrons increases, the Kramer formula deviates from the RSCF and RCI results. For instance, when the energy of the incident electron is larger than 100eV, the n-state selective cross sections of Ar7+ calculated from the Kramer formula are underestimated for more than 50%. The RSCF results are in general agreement with the RCI results. However, for the low charged ions, a clear distinction appears due to the strong configuration interaction, especially near the Cooper minimum. The n-resolved (n≤10) and total Maxwellian averaged rate coefficients are calculated, and the analytic fitting parameters are also provided.

State selective electron capture in low energy positron and argon collisions

A three-body classical trajectory Monte Carlo method is applied in the study of positron and argon atom collisions at impact energies between 10 and 60eV. The calculations are based on the independent particle model. We present state selective and total positronium formation cross sections as a function of the impact energy. Our results are compared with recent experimental data.

Measurement of the differential cross section of the photoinitiated reactive collision of O(D1)+D2 using only one molecular beam: A study by three dimensional velocity mapping

In order to measure the state selective double differential cross section of a reactive collision, the preparation of the reactants with defined initial velocities and quantum states in number densities high enough to achieve an acceptable count rate is most important. At the same time, secondary collisions have to be prevented in order to ensure that the nascent products are not thermalized. Usually, the best way to control the initial conditions is to use crossed molecular beams, but the number density decreases quadratically with the distance from the nozzle orifice which can be a problem, especially if a molecular product with a large number of populated states is to be analyzed state specifically by REMPI spectroscopy. In this contribution we would like to present a method for measuring the quantum state selective differential cross section of a photoinitiated reaction that combines the advantages of the PHOTOLOC technique (high reactant densities) and the parallel beams technique used by the groups of Kitsopoulos, Orr-Ewing, and Suits (defined relative velocity of the reactants). Moreover, an algorithm based on a Bayesian backward reconstruction developed by W. H. Richardson [J. Opt. Soc. Am. 62, 55 (1972)] has been derived. Both, one reactant and the precursor of the other reactant, are present in the same molecular beam and the center of mass velocity is selected by shifting the dissociation and the detection laser in time and space. Like in comparable methods, this produces a bias in the measured velocity distribution due to the fact that the reaction takes place in the whole volume surrounding the laser beams. This has been also reported by Toomes et al. in the case of the parallel beams technique and presents a general problem of probing reaction products by REMPI spectroscopy. To account for this, we develop a general approach that can be easily adapted to other conditions. The bias is removed in addition to deconvolution from the spread in reactant velocities. Using the benchmark system O((1)D)+D(2) with N(2)O as the precursor, we demonstrate that the technique is also applicable in a very general sense (i.e., also with a large spread in reactant velocities, products much faster than reactants) and therefore can be used also if such unfortunate conditions cannot be avoided. Since the resulting distribution of velocities in the laboratory frame is not cylindrically symmetric, three dimensional velocity mapping is the method of choice for the detection of the ionized products. For the reconstruction, the distance between the two laser beams is an important parameter. We have measured this distance using the photodissociation of HBr at 193 nm, detecting the H atoms near 243 nm. The collision energy resulting from the 193 nm photodissociation of N(2)O is 5.2+/-1.9 kcal/mol. Our results show a preference for backward scattered D atoms with the OH partner fragment in the high vibrational states (v=4-6), in accord with previously published results claiming the growing importance of a linear abstraction mechanism for collision energies higher than 2.4 kcal/mol.

Classical/quantum correspondence in state selective charge transfer and excitation reactions involving highly charged ions and hydrogen

State selective charge transfer and excitation cross sections for collisions of Neq+ (q = 1–10) with atomic hydrogen are calculated within the framework of Classical Trajectory Monte Carlo (CTMC) method and Boundary Corrected Continuum Intermediate State (BCCIS) approximation.

State selective electron capture and excitation in proton collisions with Be

An ab initio study of charge exchange and excitation processes in collisions between protons and beryllium atoms is presented. State selective cross sections are obtained for collision energies between 2.5 × 10−7 and 16 keV/amu, using both quantum and semiclassical treatments. A very large isotopic dependence of the charge exchange cross section is found at energies below 0.6 eV/amu.