共查询到20条相似文献,搜索用时 273 毫秒
1.
The asymmetry of the natural line profile for transitions in hydrogenlike atoms is evaluated within a QED framework. For the Lyman- alpha 1s-2p absorption transition in neutral hydrogen this asymmetry results in an additional energy shift of 2.929 856 Hz. For the 2s(1/2)-2p(3/2) transition it amounts to -1.512 674 Hz. As a new feature this correction turns out to be process dependent. The quoted numbers refer to the Compton-scattering process. 相似文献
2.
Weber G Bräuning H Surzhykov A Brandau C Fritzsche S Geyer S Hagmann S Hess S Kozhuharov C Märtin R Petridis N Reuschl R Spillmann U Trotsenko S Winters DF Stöhlker T 《Physical review letters》2010,105(24):243002
We report the observation of an interference between the electric dipole (E1) and the magnetic quadrupole (M2) amplitudes for the linear polarization of the Ly-α1 (2p3/2→1s1/2) radiation of hydrogenlike uranium. This multipole mixing arises from the coupling of the ion to different multipole components of the radiation field. Our observation indicates a significant depolarization of the Ly-α1 radiation due to the E1-M2 amplitude mixing. It proves that a combined measurement of the linear polarization and of the angular distribution enables a very precise determination of the ratio of the E1 and the M2 transition amplitudes and the corresponding transition rates without any assumptions concerning the population mechanism for the 2p3/2 state. 相似文献
3.
Stohlker T Mokler PH Bosch F Dunford RW Franzke F Klepper O Kozhuharov C Ludziejewski T Nolden F Reich H Rymuza P Stachura Z Steck M Swiat P Warczak A 《Physical review letters》2000,85(15):3109-3112
The Lyman- alpha transitions of hydrogenlike uranium associated with electron capture were measured in collisions of stored bare U (92+) ions with gaseous targets at the storage ring ESR. By applying the deceleration technique, the experiment was performed at slow collision energies in order to reduce the uncertainties associated with Doppler corrections. From the measured centroid energies, a ground state Lamb shift of 468 eV+/-13 eV is deduced which gives the most precise test of quantum electrodynamics for a single electron system in the strong field regime. In particular, the technique applied paves the way towards the 1 eV precision regime. 相似文献
4.
在相对论多组态Dirac-Fock方法和密度矩阵理论的基础上,利用发展的全相对论扭曲波程序,系统研究了超精细结构效应对纵向极化电子碰撞激发过程以及退激发辐射光谱圆极化特性的影响.计算得到了类氦Sc~(19+)和~(205)Tl~(79+)离子1s~2 ~1S_0→1s2p ~3P_2超精细结构层次上M_F能级的碰撞强度,考察了辐射衰变过程中发出特征光子的极化特性,并分析了E1-M2量子干涉效应以及电子-电子间相互作用的相对论修正对退激发辐射光子圆极化度的影响. 相似文献
5.
V. N. Peregudov 《Hyperfine Interactions》1977,3(1):353-360
It is shown that interference effects in Mössbauer transmission experiments with pure E2 and mixed E2/M1 transitions are, generally, due to interference between the internal conversion and the photoeffect. This interference effect is mainly determined by the quadrupole part of the photoabsorption, which is comparable to the dipole part at transition energies of about 100 keV. A noticeable part of the interference effect in the case of E2 transitions can be attributed to the interference between the nuclear resonant scattering and Rayleigh scattering on atomic electrons. The angular distribution of the (, e) reaction cross section has been calculated for E2 transitions. 相似文献
6.
The 1S-2P transition in atomic hydrogen has been observed for the first time with almost natural linewidth. We employ a unique source of continuous coherent Lyman- alpha radiation based on four-wave mixing in mercury. The output of the source has been improved 40-fold to yield 20 nW. This demonstration shows that laser cooling and detection with continuous Lyman- alpha radiation has excellent prospects for future experiments with antihydrogen. 相似文献
7.
Rajesh Kharab Pardeep Singh Ravinder Kumar 《中国物理快报》2007,24(3):656-659
We investigate the effects of higher order multipole transitions, in particular electric quadrupole (E2) and El-E2 interference, on the Coulomb dissociation of 19 C within the framework of the first order eikonal approximation. The sensitivity of the total Coulomb breakup cross section and the longitudinal momentum distribution of the core fragment to these effects are checked. The breakup occurs predominately through the dipole transition and the contribution of E2 transition to the total cross section is found to be within the range from 1 to 3% of that of El. It is further observed that the El-E2 interference term contributes nothing to the integrated cross section. On the other hand, the longitudinal momentum distribution is observed to be insensitive to the E2 transition while the El-E2 interference introduces a small asymmetry in its shape. 相似文献
8.
P. Indelicato S. Boucard E. Lindroth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):29-41
We report on a calculation of K, L and M inner-shell ionization energy in atoms with atomic numbers in the range . Many-body effects are evaluated for all n
=1, 2, and 3 hole states. Those include correlation and effects due to the auto-ionizing nature of the hole states (Auger shift). For
high Z we add recent corrected nuclear polarization, and several second-order vacuum polarization corrections. K and L ionization
energies are compared with experimental X-ray absorption edges measurements. Excellent agreement with rare gazes and metal
vapor measurements is found. We also compare our calculations with X-ray transition energies for all K and L lines that involve
K, L and M holes. Finally we use K X-ray lines to deduce an hydrogenlike 1
s Lamb shift for several heavy elements, with far better accuracy than has been obtained by direct measurements of hydrogenlike
ions.
Received: 25 February 1998 / Accepted: 31 March 1998 相似文献
9.
It is proposed to apply the radiative electron capture into high-Z projectiles as a probe process for measuring the spin polarization of the hydrogenlike ions at storage rings. We argue that such polarization measurements are possible since the linear polarization of emitted x-ray photons is greatly sensitive to the spin states of incoming ions with nuclear spin I > 1/2. In particular, for K-shell electron capture into the hydrogenlike ions, the linear polarization of light as measured out of the reaction plane is found to be proportional to the degree of ion polarization. Detailed computations for the dependence of the photon polarization on the ion spin states and projectile energies are carried out for the electron recombination into hydrogenlike Bi 82+ ions. 相似文献
10.
Expansion and disasembly phase of energetic nuclear reactions: A problem of dynamical instabilities?
Lyman α transitions emitted from hydrogenlike Ar recoil ions investigated by high resolution crystal diffraction spectroscopy show noticeable influence of spectator electrons. Theoretical values for the 2p-1s transition energies were confirmed to approximately the 100 ppm level of the data. 相似文献
11.
The direct-semidirect model for nucleon radiative capture proceeding via giant E1 and E2 resonance states is extended to account for capture through collective M1 excitation. The 208Pb(N, γ0) and 140Ce(N, γ0) reactions are investigated in the 2–10 MeV energy interval. For the M1 and isoscalar E2 neutron capture processes, calculations provide cross section values of the same order of magnitude, as well as comparable effects on γ-ray angular distributions. The model proves to be an appropriate framework for discussing the E1-M1 and E1-E2 interference processes, giving useful suggestions as to effects arising from the presence of the M1 and E2 collectivities. 相似文献
12.
Litvinov YA Bosch F Geissel H Kurcewicz J Patyk Z Winckler N Batist L Beckert K Boutin D Brandau C Chen L Dimopoulou C Fabian B Faestermann T Fragner A Grigorenko L Haettner E Hess S Kienle P Knöbel R Kozhuharov C Litvinov SA Maier L Mazzocco M Montes F Münzenberg G Musumarra A Nociforo C Nolden F Pfützner M Plass WR Prochazka A Reda R Reuschl R Scheidenberger C Steck M Stöhlker T Torilov S Trassinelli M Sun B Weick H Winkler M 《Physical review letters》2007,99(26):262501
We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay. 相似文献
13.
The hyperfine structure (hfs) of electron levels of 23892U ions with the nucleus excited in the low-lying rotational 2(+) state with an energy E(2(+)) = 44.91 keV is investigated. In hydrogenlike uranium, the hfs splitting for the 1s(1/2) ground state of the electron constitutes 1.8 eV. The hyperfine-quenched (hfq) lifetime of the 1s2p 3P0 state has been calculated for heliumlike 23892U and was found to be 2 orders of magnitude smaller than for the ion with the nucleus in the ground state. The possibility of a precise determination of the nuclear g(r) factor for the rotational 2(+) state by measurements of the hfq lifetime is discussed. 相似文献
14.
基于多组态Dirac-Fock方法和密度矩阵理论,系统地研究了在197 Me V/u的碰撞能量下,Xe~(53+)离子与Xe原子的辐射电子俘获过程(REC)以及电子被俘获到激发态后辐射退激发产生的特征谱线.计算了炮弹Xe~(53+)离子俘获电子到不同壳层np_(1/2,3/2)(n=2—5)的总截面与相应的REC光子能量和角分布,以及由激发组态1snp_(1/2,3/2)(n=2—5)J_f=1向基态1s~2Jd=0辐射退激发的跃迁能量、跃迁概率和特征光子的角分布和线性极化度.计算结果表明,辐射光子具有显著的角各向异性特征.此外,1snp_(3/2)J_f=1→1s~2J_d=0退激发特征光子也显示出很强的线性极化和角各向异性特征,而1snp_(1/2)J_f=1→1s~2J_d=0退激发特征光子的线性极化度趋于零并且角分布也趋于各向同性. 相似文献
15.
R. Kotte E. Hentschel H. -G. Ortlepp W. Seidel F. Stary 《Zeitschrift für Physik A Hadrons and Nuclei》1987,328(4):495-496
Ternary fission has been investigated by irradiating a natural uranium target with 13.5 MeV deuterons. The energy and angular distributions of ternary alpha particles do not differ from those observed in spontaneous or thermal neutron induced fission. The angle between alpha particles and light fragments has a most probable value of \(\bar \vartheta _{\ell f - \alpha } = 82.1 \circ \pm 0.6 \circ \) with a dispersion (FWHM) of \(\Delta \vartheta = 18.4 \circ \pm 1.2 \circ \) . The corresponding values of the energy distribution are \(\bar E\alpha \) =(14.8 ±0.5)MeV and ΔE(FWHM)= (9.1±1.1)MeV. The peak-to-valley ratio of the ternary fission fragment mass distribution is found to increase with increasing alpha energy. For near-symmetric mass division a strong broadening of the angular distribution is observed. 相似文献
16.
R. Kotte W. D. Fromm E. Hentschel H. G. Ortlepp K. D. Schilling W. Seidel F. Stary G. Zwicker 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(2):189-195
Nuclear fission accompanied by long-range alpha particles has been investigated. Fission was induced by irradiating a natural uranium target with 13.5 MeV deuterons. The alpha energy and angular distributions are similar to those observed in spontaneous or thermal neutron induced fission. The correlation angle between alpha particles and light fission fragments has a most probable value of \(\bar \vartheta _{l f - \alpha } = 82.1^\circ \pm 0.9^\circ \) and a dispersion (FWHM) of Δ?=18.4°±1.2°. The mean value and dispersion of the energy distribution are \(\bar {\rm E}_\alpha = 14.8 \pm 1.0 MeV\) and ΔE=9.1±1.2 MeV (FWHM), respectively. The peak-to-valley ratio of the ternary fission fragment mass distribution is found to increase with increasing alpha energy. For near-symmetric mass division, a strong broadening of the angular distribution is observed. The results are discussed in the frame of a multichannel-fission model. 相似文献
17.
18.
Angular distributions of photoprotons following the (e, e′p) reaction in 208Pb have been measured at incident energies of 25.0 MeV and 40.0 MeV. The proton energy distributions were measured at several angles and the angular distributions were obtained for several proton energy ranges. Proton groups at around 11.0 MeV and 15.3 MeV are separated for the angular distributions and the results show almost isotropic distributions, which indicate that these proton groups are emitted through IAR. The angular distributions for other slowly varying parts of the proton spectra proved strongly asymmetrical, indicative of interference between E1 and E2 transition. 相似文献
19.
R. Tielert H. H. Bukow P. H. Heckmann R. Woodruff H. v. Buttlar 《Zeitschrift für Physik A Hadrons and Nuclei》1973,264(2):129-138
Relative initial populations of foil-excited hydrogen atoms in the2p, 3s, 3p, and3d states are determined by measuring the Balmer-α and Lyman-α emissions simultaneously. The data are analyzed by a computer program which takes into account the correlation of both emissions. The results show a dependence on the kind of incident ions: molecular ions give more light and lead to more pronounced excitation of higher angular momentum states than do atomic ions. A possible mechanism to explain this “molecule effect” is discussed qualitatively. 相似文献