共查询到20条相似文献,搜索用时 15 毫秒
1.
Edward J Kelsey 《Annals of Physics》1976,98(2):462-489
The order (Zα)5, α(Zα)4, and α(Zα)4 log(Zα) energy denominator and recoil corrections to the leading order (Zα)4 decay amplitude for the 23S1 → 11S0 + one photon transition are considered. It is found that order α(Zα)4 terms arise in the individual diagrams but exactly cancel upon summation. In view of the results of this and other recent theoretical work it is concluded that the rates predicted by pure quantum electrodynamics are known to considerable precision. The recent discrepancy between theory and experiment in the decay rate for several helium-like ions appears to have been resolved by placing the detector farther downstream from the foil where the metastable states are produced. At present, all the experimental values are in good agreement with the theory. 相似文献
2.
Based cn the relativistic Bethe-Salpeter (BS) equation, the positronium wavefunctions in Euclidean momentum space are obtained. Meanwhile the energy levels of positronium ground states 11S0 and 13S1 are fitted to be 6.7934 eV and 6.7929 eV respectively, which qualitatively agree with the previous theoretical values. It is shown that the BS theory is valid and reliable to treat positronium. 相似文献
3.
Based on the relativistic Bethe-Salpeter
(BS) equation, the positronium
wavefunctions in Euclidean momentum space are obtained. Meanwhile the energy
levels of positronium ground states
11S0
and 13S1
are fitted to be 6.7934 eV and
6.7929 eV respectively, which qualitatively agree with the
previous theoretical values. It is shown that the BS theory is valid and
reliable to treat positronium. 相似文献
4.
PrF3 as well as PrF3-LiF and PrF3-MgF2 mixtures were investigated by means of high-energetic excitation with synchrotron radiation. In the PrF3 emission spectrum bands due to the intra-configurational 4f24f2 transitions originating from the 1S0 level of the Pr3+ ion have been identified. The emission from the 3P0 multiplet is very weak due to non-radiative decay by cross-relaxation processes. Therefore, PrF3 is not an efficient direct cascade emitter. In the PrF3 excitation spectra in the ultraviolet/vacuum-ultraviolet spectral range, the 3H41S0 transition at 46858 cm-1 as well as broad bands due to the inter-configurational 4f24f5d transitions are observed. By comparison with data of Pr3+ doped YF3, the branching ratios of the emission transitions for PrF3 from the 1S0 were determined; these are 0.008, 0.075, 0.262, 0.023 and 0.629 for transitions 1S03H4, 3F4, 1G4, 1D2 and 1I6, respectively. For the polycrystalline PrF3-LiF and PrF3-MgF2 samples investigated by us, the measured emission and excitation spectra are nearly identical
to those of PrF3. For polycrystalline PrF3-KMgF3 the observed spectra are superpositions of the PrF3 and Pr3+:KMgF3 spectra. PACS 42.70.-a; 78.55.-m; 78.55.Hx 相似文献
5.
6.
Wiedeking M Fallon P Macchiavelli AO Gibelin J Basunia MS Clark RM Cromaz M Deleplanque MA Gros S Jeppesen HB Lake PT Lee IY Moretto LG Pavan J Phair L Rodriguez-Vietiez E Bernstein LA Bleuel DL Burke JT Lesher SR Lyles BF Scielzo ND 《Physical review letters》2008,100(15):152501
The lifetime of the 2_+(1) state in 16C has been measured with the recoil distance method using the 9Be(9Be,2p) fusion-evaporation reaction at a beam energy of 40 MeV. The mean lifetime was measured to be 11.7(20) ps corresponding to a B(E2;2_+(1)-->0+) value of 4.15(73)e_2 fm_4 [1.73(30) W.u.], consistent with other even-even closed shell nuclei. Our result does not support an interpretation for "decoupled" valence neutrons. 相似文献
7.
8.
In this paper we present and discuss results of detailed spectroscopy studies of Pr3+ luminescence from the (Ba,La)F2:0.2 m%Pr crystals under UV and VUV synchrotron excitation.We have measured time resolved emissions from the minor site Pr3+ in (Ba,La)F2:Pr at 10 and 300 K. The spectra clearly show the 1S0 emission from the Pr3+ ions in some low symmetry Pr-sites (we designate them La-sites) previously identified in higher concentration (0.3 m%Pr and more) crystals. However most of emission from the Pr activated (Ba,La)F2 crystals originates in Pr3+ ions in other sites which produce an efficient d-f emission. As demonstrated by excitation spectra, the emission from some of these sites (denoted as Ba-sites) closely resembles the d-f emission from BaF2.The La-site, time resolved and long delay emission spectra are dominated by hypersensitive transitions from the 1S0 and 3P0 levels to lower energy levels of the 4f2 configurations. Only these transitions contribute to the photon cascade emission desired for some mercury free phosphor applications. 相似文献
9.
V. A. Schegelsky A. V. Sarantsev V. A. Nikonov A. V. Anisovich 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):207-212
The K0
SK0
S final state in two-photon collisions is studied with the L3 experiment at LEP, using orbital angular momentum operators.
The mass spectrum is dominated by the formation of tensor mesons, their two-photon partial width are determined. A signal
at 1700-1800MeV is found to be a new tensor state f
2(1750) with mass M = (1755±10)MeV and width Γ = (67±12)MeV. All observed tensor resonances obey SU(3) relations. The f
2(1750) state forms a second tensor nonet together with f
2(1560) and a
2(1700). The SU(3) analysis allows us to determine with good accuracy mixing angles between nonstrange and strange components of the isoscalar
members of tensor nonets. 相似文献
10.
11.
12.
Petri M Fallon P Macchiavelli AO Paschalis S Starosta K Baugher T Bazin D Cartegni L Clark RM Crawford HL Cromaz M Dewald A Gade A Grinyer GF Gros S Hackstein M Jeppesen HB Lee IY McDaniel S Miller D Rajabali MM Ratkiewicz A Rother W Voss P Walsh KA Weisshaar D Wiedeking M Brown BA 《Physical review letters》2011,107(10):102501
Establishing how and when large N/Z values require modified or new theoretical tools is a major quest in nuclear physics. Here we report the first measurement of the lifetime of the 2(1)+ state in the near-dripline nucleus 20C. The deduced value of τ(2(1)+)=9.8±2.8(stat)(-1.1)(+0.5)(syst) ps gives a reduced transition probability of B(E2; 2(1)+→0(g.s.)+)=7.5(-1.7)(+3.0)(stat)(-0.4)(+1.0)(syst) e2 fm4 in good agreement with a shell model calculation using isospin-dependent effective charges. 相似文献
13.
14.
The intensity-dependent transmission of picosecond ruby laser pulses of different duration through methanolic and ethanolic solutions of rhodamine B and rhodamine 6G is analysed. The transmission is affected by S0-S
n
two-photon absorption, by stimulated emission at the pump-laser frequency, by amplified spontaneous emission and by excited-state absorption. Various parameters involving the two-photon absorption dynamics are determined by comparing experiments with numerical simulations. 相似文献
15.
16.
B. Huber 《Zeitschrift für Physik A Hadrons and Nuclei》1976,277(1):31-33
Total and differential cross sections for the production of fast Kr2+ ions in collisions of He+, Ne+ and Ar+ with Kr were measured at primary energies below 500 eV. In the system Ar++Kr most of these reactions occur in close collisions and are accompanied by a large momentum transfer. For Ne++ Kr collisions the angular distribution in the centre of mass system is approximately isotropic over a wide angular range. The cross section values for the Kr2+ production amount to 1% of the total charge transfer cross section in the investigated energy range. 相似文献
17.
Abe F Akimoto H Akopian A Albrow MG Amendolia SR Amidei D Antos J Anway-Wiese C Aota S Apollinari G Asakawa T Ashmanskas W Atac M Azfar F Azzi-Bacchetta P Bacchetta N Badgett W Bagdasarov S Bailey MW Bao J de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Barzi E Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Benton D Beretvas A Berge JP Berryhill J Bertolucci S Bhatti A Biery K Binkley M Bisello D Blair RE Blocker C Bodek A 《Physical review letters》1996,77(8):1439-1443
18.
Previous work [Moss, R. E., and Valenzano, L., 2002, Molec. Phys., 100, 649 and 1527] on the non-adiabatic properties of the vibration-rotation levels of the ground electronic state of the hydrogen molecular cation is extended to the calculation of relativistic corrections. Unlike the earlier calculations, in which all matrix elements were evaluated analytically, numerical methods are needed for some of the integrals. 相似文献
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20.
The 5S1/2 --> 7S1/2 two-photon transition of atomic rubidium, which is 100 times weaker than the 5S-5D transition, is observed with an extended-cavity diode laser and a vapor cell. Signals with a signal-to-noise ratio of 280 are obtained with a laser power of 10 mW, and the observed linewidth is 3 MHz. The laser wavelength is 760 nm and is locked on the transitions to a stability of 2 x 10(-11). For the first time to our knowledge, the isotope shift of this transition is measured to be 130(4) MHz in atomic frequency. 相似文献