钪原子的自电离里德伯能级3d4s(~1D_2)nf~2D_(3/2),3d4s(~1D_2)nf~2F_(5/2)和3d4s(~1D_2)np~2D_(3/2)的理论研究

在多通道量子亏损理论框架下,利用相对论多通道理论,分别在冻结实近似和考虑偶极极化下计算钪原子的Jπ=(3/2)-,(5/2)-的三个收敛于[Ar]3d4s(1D2)的自电离里德伯系列的能级.对3d4s(1D2)np2D3/2和3d4s(1D2)nf2F5/2这两个系列,计算结果表明,考虑偶极极化效应后,理论计算和实验测量的量子数亏损之差普遍小于0.01.而对3d4s(1D2)nf2D3/2系列,考虑偶极极化效应后的结果和仅考虑冻结实的结果比较接近,理论计算和实验测量的量子数亏损之差普遍在0.04左右.     

Natural radiative lifetimes in the2S1/2 and2D5/2,3/2 sequences of aluminum

Natural radiative lifetimes have been measured for the 3s ² ns ² S _1/2 (n≦10) and 3s ² nd ² D _5/2,3/2 (n≦11) sequences of aluminum using pulsed laser excitation of an atomic beam. The investigated states were populated from the ground configuration using UV pulses of wavelength down to 210 nm produced by a Nd: YAG- or an excimer-pumped dye-laser system. TheS-state lifetimes increase regularily with increasing principal quantum number but this is not the case for theD sequence.     

Lebensdauer und Hyperfeinstrukturaufspaltung der Terme 4d5s5p y2D3/2,5/2 und 4d5s5p y2F5/2,7/2 im Yttrium I Spektrum

With level crossing technique the states 4d5s5p y²D_3/2,5/2 and 4d5s5p y²F_5/2,7/2 in the Yttrium I spectrum were investigated and the magnetic hyperfine structure splitting A factors and the lifetimes determined. The experimental values are discussed and compared with theoretical results.     

Measurement of the electric quadrupole moment of the 4d2D5/2 level in 88Sr+

The quadrupole moment of the 4d (2)D(5/2) level in 88Sr+ has been measured to be 2.6(3)ea(2)(0), where a(0) is the Bohr radius and e the elementary charge. A single laser-cooled strontium ion was confined in an end cap trap with a variable dc quadrupole potential, and measurements were made on the 5s (2)S(1/2)-4d (2)D(5/2) transition at 674 nm using a femtosecond optical frequency comb. This work shows that measurements of the unperturbed 88Sr+ transition frequency with sub-Hz uncertainty are possible and is important in understanding the reproducibility of ion trap optical frequency standards.     

Hyperfine structure and isotope shifts in the 5d6s2 a2D3/2--5d6s(a3D)6p z4F5/2 ° transition of Hf II

The hyperfine structure and isotope shifts of the transition between the 5d6s² a²D_3/2 ground state and the 5d6s(a³D)6p z⁴F_5/2 ^° excited state of singly ionized hafnium at \lambda=340 nm have been investigated by laser spectroscopy using a radio-frequency quadrupole ion trap. The magnetic dipole coupling constant A and electric quadrupole coupling constant B of the two atomic levels for both stable isotopes ¹⁷⁷Hf and ¹⁷⁹Hf are determined. The changes of mean square nuclear charge radii \delta[ r²] of the stable Hf isotopes and the radioactive isotope ¹⁷²Hf (T_1/2=1.87a) have been extracted from the data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nondipole effects in the photoionization of xe 4d5/2 and 4d3/2: evidence for quadrupole satellites

Measurements of nondipole parameters in spin-orbit-resolved Xe 4d photoionization demonstrate dynamical differences arising from relativistic effects. The experimental data do not agree with relativistic random-phase approximation calculations of single ionization dipole and quadrupole channels. It is suggested that the discrepancy is due to the omission of multiple-excitation quadrupole channels, i.e., quadrupole satellite transitions.     

1D and 2D solid state NMR investigations of the framework structure of As-synthesized AlPO4-14

The framework structure of As-synthesized A1PO₄-14 has been investigated with a combination of different one-dimensional ²⁷Al and ³¹P solid state NMR techniques and ²⁷Al/³¹P double resonance methods. The results are found to be fully consistent with the assumed structural model. ²⁷Al MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral sites, one pentacoordinated and one octahedral aluminum site. The ²⁷Al quadrupolar coupling constants and the ³¹P isotropic chemical shifts of the tetrahedral sites correlate well with tetrahedral shear-strain parameters and mean P-O-A1 bond angles, respectively. These correlations allow one to assign all of the NMR resonances to specific T-sites in the proposed framework structure. The assignments are then further confirmed by the application of three different two-dimensional heteronuclear correlation methods (i.e., ²⁷Al → ³¹P TEDOR, CP, and INEPT) which reveal the connectivities between AlO_x and PO₄ polyhedra. The two-dimensional INEPT experiment is applied here for the first time in the solid state.     

Stark-Effekt-Untersuchungen der Hyperfeinstruktur der 5s25d2D3/2- und 5s25d2D3/2-Terme im In I-Spektrum

The level-crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure of the 5s ²5d ² D _3/2- and 5s ²6d ² D _3/2-stedes of the In I-spectrum. From the shifts of the level-crossing signals due to the Stark effect of the electric field the Stark constantsβ of both states were deduced: 5s ²5d ² D _3/2: ¦β¦=0.33(3) Mc/(kV/cm)² 5s ²6d ² D _3/2: ¦β¦=6(1) Mc/(kV/cm)². By theoretical calculations with wave functions of the Coulomb approximation one can show, that the Stark effect in both states is mainly due to admixtures of the 5s ²6p- resp.5s ²7p-configuration.     

Mode-crossing signals of high order on the 4d 95s 2 2 D 5/2 state of Cd II isotopes

In the linearly polarized radiation field of a 442 nm He-Cd laser containing a natural isotope mixture, saturation-induced mode-crossing signals of the 4d ⁹5s ^{2 2} _5/2 state of Cd II are observed due to the even as well as the odd isotopes. The signal width of about 10^?4 T yields high resolution. Thus the signal splitting respective to the magnetic quantum number can be resolved. Theg _J - andg _F -factors of the² D _5/2 state are determined as follows:g _J=1.1980±0.0036,g _F(F=2)=1.397±0.008,g _F(F=3)=1.002±0.009.     

Life-times of the 4 1 + -states in134Te and136Xe

The half-lives of the first excited 4⁺-levels in theN=82 isotones ₅₂ ¹³⁴ Te and ₅₄ ¹³⁶ Xe have been determined tot _1/2=(1.50±0.13) ns andt _1/2=(1.32±0.10) ns, respectively, through the measurement of delayedγ,γ-coincidences. The value for¹³⁴Te is in agreement with the assumption that the low lying levels of this nucleus are based mainly on theg ₇ ^{2 /2} proton configuration. In¹³⁶Xe the half-life is unexpectedly small which indicates a more strongly admixed structure of the levels involved in this case.     

Isotope shift and hyperfine structure of the transition5d6s 2 2 D 3/2-5d6s6p 4 F 3/2 of Lu175 and Lu176

Using a tunable single mode dye laser the isotope shift of the 573.7 nm-line between the isotopes Lu¹⁷⁵ and Lu¹⁷⁶ has been determined to be IS(176?175, 573.7 nm)=?394(5) MHz yielding a change of mean square nuclear radii ofδ〈r ²〉=0.022(5) fm². In addition from our measurements the following values of the hyperfine splitting constantsA andB could be deduced Lu¹⁷⁶ 5d6s6p ⁴ F _3/2:A=?651.4(0.3) MHz,B=2,494(4) MHz 5d6s ^{2 2} D _3/2:A=138.0(0.3) MHz,B=2,131(3) MHz Lu¹⁷⁵ 5d6s6p ⁴ F _3/2:A=?924.7(0.5) MHz,B=1,767(4) MHz.     

Mixing of atomic barium states 6s5d 3 D 1 and 6s5d 3 D 2 by laser radiation

Experimental studies of perturbation of atoms by laser radiation under conditions when, due to the Stark effect, the energies of two neighboring levels become equal are reported for the first time.     

Lande g-Factors of 7d1D2 and 8d1D2 States of Mercury

Lande g-factors of 5d¹⁰6s7d¹D₂(1.0155) and 5d¹⁰6s8d¹D₂(1.0285) atomic mercury levels have been determined using quantum beats method after electron pulse excitation.     

Level crossing measurement of the 32 D fine structure of lithium

The fine structure splitting of the 3² D-state of lithium was measured using the level crossing technique with delayed observation. Two nitrogen laser pumped dye lasers were used for a stepwise excitation. The linewidth observed was 40% smaller than the natural width. The result derived for the splitting is (1080.1±1.0)MHz.     

Level-Crossing-Experimente zur Untersuchung der Hyperfeinstruktur des 5d 2 D 5/2-Terms im Indium I-Spektrum

The resonance fluorescence of the transition 5d ² D _5/2?5p ² P _3/2 (λ=3256Å) in the In I-spectrum was observed as a function of an external magnetic field. From the level crossing signals the following values of the hyperfine constantsA andB of the 5d ² D _5/2-state were deduced: ¦A¦=148(8) Mc/sec·g _J/1.2 and ¦B/A¦≦0.3. The widths of the signals yielded the mean lifetimet=7.1 (6)·10^?9 sec · 1.2/g _J . From the shifts of the signals caused by a constant electric field parallel to the magnetic field the value of the Stark parameter ¦β¦=0.19(4) Mc/sec/(kV/cm)² ·g _J /1.2 and the sign of the ratioA/β<0 were determined. Calculations with Coulomb wave functions show that the Stark shifts of the electric field are mainly due to admixtures of the 6p ² P _3/2-state.