铀原子自电离态能级测量

用三台可调谐脉冲染料激光器三步共振电离方法,测量了在４９８９８－５０８８０ｃｍ＾－１能量区间的一些轴原子里堡态和自电离态能级位置。     

Lifetimes of excited levels of Kr I and Kr II

The lifetimes of eight levels belonging to the 6p configuration of KrI and thirteen levels belonging to different configurations of KrII have been measured. The levels were excited by short electron pulses of appropriate energy and the lifetimes determined by a delayed coincidence method using single photon counting techniques. All measurements were carried out at different gas pressures. The measured lifetimes of the KrII levels are compared with other experimental results obtained by a different method (beam-foil spectroscopy) and with calculations made in the intermediate coupling scheme.     

Some lifetimes and transition probabilities in Cu(I)

Radiative lifetimes of 7 levels in the Cu(I) 3d⁹ 4s4p configuration have been measured using a delayed coincidence technique; copper vapor was excited in an argon buffer gas and cross sections for collisional destruction of copper levels by argon were also obtained. Transition probabilities of the lines originating from these levels have been determined using the measured lifetimes and branching ratios.     

Radiative lifetimes of Rydberg 6pnd J=2 states of Pb I by multichannel quantum defect theory

Energy levels of the odd-parity 6pnd J=2 Rydberg states of Pb I are analysed by the multichannel quantum defect theory (MQDT) in the frame of a five-channel three-limit calculation model. With optimal MQDT parameters, channel admixture coefficients are obtained and used to calculate the theoretical lifetimes of the levels by comparing to the previously measured lifetimes. The predicted lifetimes for higher-lying Rydberg states are given and discussed. These predicted lifetimes are very different from those obtained by the four-channel two-limit model pl:eviously used, which means that introduction of the additional interacting channel is important for studying the 6pnd J=2 Rydberg states of Pb I.     

Investigation of electron lifetimes in molybdenum with dilute substitutional impurities

We have measured the electronic lifetimes of the systems Mo(W), Mo(Ru), Mo(Fe) and Mo(U). The concentrations were ≈ 370PPM, 70PPM, 20PPM, and 50PPM respectively. For the first three systems, only the hole octahedron centered atH was investigated thoroughly for all angles and the data inverted to get point lifetimes. For Mo(U) the investigation was done over the entire Fermi surface with the aid of an on-line PDP 11/20 mini-computer. Only selective points were used on other pieces of the Fermi surface in order to avoid problems with degenerate frequencies. A careful determination of the effective masses was also made at all angles under investigation. The masses were found to be in disagreement with those of Leaver and Meyers (these masses were used in our orginal investigation) by as much as 20% in some orientations. The electronic lifetimes were nearly isotropic on the hole octahedron in all the alloy systems investigated. In Mo(U) the isotropy was found to extend to all thed-like surfaces. Only thes-p-like hole ellipsoids centered atN possibly have a substantially different lifetime, but its measurement is inaccurate due to beats from degenerate and many close-lying frequencies.     

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Data on classification of spectra and energy levels of atoms of rare earth elements with unfilled 4f-shells have been collected, systematized and analyzed. A brief account is given of methods for determining transition probabilities and lifetimes of the excited states of atoms and ions. Oscillator strengths for spectral lines of Nd(I), Sm(I), Eu(I), Gd(I), Dy(I), Tm(I) and Yb(I) have been measured using Rojdestvensky's hook method. Lifetimes of some of the excited states of Eu(I), Yb(I) and Yb(II) have been determined by using simultaneously the methods of delayed coincidence, hooks, and total absorption. Our results have been compared with those of other investigators. Atoms with unfilled 4f-shells show some regularities.     

Investigation of electron lifetimes in molybdenum with dilute substitutional impurities

We have measured the electronic lifetimes of the systems Mo(W), Mo(Ru), Mo(Fe) and Mo(U). The concentrations were 370PPM, 70PPM, 20PPM, and 50PPM respectively. For the first three systems, only the hole octahedron centered atH was investigated thoroughly for all angles and the data inverted to get point lifetimes. For Mo(U) the investigation was done over the entire Fermi surface with the aid of an on-line PDP 11/20 mini-computer. Only selective points were used on other pieces of the Fermi surface in order to avoid problems with degenerate frequencies. A careful determination of the effective masses was also made at all angles under investigation. The masses were found to be in disagreement with those of Leaver and Meyers (these masses were used in our orginal investigation) by as much as 20% in some orientations. The electronic lifetimes were nearly isotropic on the hole octahedron in all the alloy systems investigated. In Mo(U) the isotropy was found to extend to all thed-like surfaces. Only thes-p-like hole ellipsoids centered atN possibly have a substantially different lifetime, but its measurement is inaccurate due to beats from degenerate and many close-lying frequencies.Work performed under the auspices of the U. S. Atomic Energy Commission.     

Short lifetimes in 26Al

Mean lifetimes of levels in ²⁶Al have been measured using the Doppler-shift attenuation (DSA) method and the reaction ²⁵Mg(p, γ)²⁶Al. The lifetime values or limits were determined for 34 bound levels below the excitation energy of 6 MeV; the lifetimes of 13 levels and upper limits of 3 levels are reported for the first time. For the effective stopping of recoils, the targets were prepared by implanting ²⁵Mg into Ta backings. The Monte Carlo method and the experimental stopping power were used in the DSA analysis.     

Oscillator strengths of neutral and singly ionised molybdenum

Oscillator strengths of 174 Mo(I) and 58 Mo(II) lines in the range 2470–5570 Å were obtained from wall-stabilised arc and hollow cathode measurements. Sets of relative f-values were determined by a combination of hook and emission measurements requiring no assumptions concerning the plasma state. The sets have been enlarged considerably by evaluating spectra recorded with a Fourier spectrometer. The relative Mo(I) f-values were converted to an absolute scale by means of radiative lifetimes measured by P. Zimmermann and his group. The overall uncertainties are within 10–35%. Since lifetimes of Mo(II) levels are not yet available, only relative Mo(II) f-values are presented.     

Radiative lifetimes of some excited states of neutral xenon

The radiative lifetimes of ten levels belonging to the nf (n=4-7) and three levels belonging to the ns (n=8,9) configuration of XeI have been measured using the high frequency deflection technique together with a delayed coincidence single-photon counting arrangement. Lifetimes of some of the levels have been measured for the first time. The results have been compared with other experimental and theoretical values.     

Short lifetimes in 38Ar

Mean lifetimes of levels in ³⁸Ar have been measured using the Doppler-shift-attenuation (DSA) method and the reaction ³⁷Cl(p, γ)³⁸Ar. The lifetime values or limits were determined for 37 bound levels below the excitation energy of 9 MeV; the lifetimes of 9 levels, upper limits of 2 and lower limits of 3 levels are reported for the first time. For the effective stopping of recoils, the targets were prepared by implanting ³⁷Cl into Ta backings. The Monte Carlo method and the experimental stopping power were used in the DSA analysis.     

Radiative lifetimes in Zr I using a novel atomic beam source

Radiative lifetimes have been measured for 15 levels of Zr I with the single photon counting method using a specially developed source. The results essentially confirm the recent lifetime measurements by Hannaford and Lowe (1981).     

Lifetimes,branching ratios,and transition probabilities in Mo I

The radiative lifetimes of 56 levels in Mo I have been measured by the method of laser-induced fluorescence from sputtered metal vapor. Emission branching ratios have been measured for these levels to determine transition probabilities for 570 Mo I transitions in the wavelength range 2944–9767 Å. The uncertainty in the transition probability of stronger branches is typically less than 5%.     

Shape evolution and test of the critical-point symmetry X(5) in 176Os

The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20h level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.     

The luminescence properties of 2-isopropoxyphenyl-N-methyl carbamate

The fluorescence and phosphorescence properties of 2-isopropoxy phenyl-N-methyl carbamate, [formula (I)], have been studied in polar and non-polar solvents, at room temperature

and at 77 K. The fluorescence quantum yield of (I) in cyclohexane at room temperature, and the ratio of phosphorescence to fluorescence yield in three solvents at 77 K have been determined. Polarization studies have been carried out on both the fluorescence and phosphorescence emission. Phosphorescent lifetimes, τ_p, have been measured in various solvents and were found to be non-single exponential in all cases. The data provides an understanding of the excitation and emission processes in (I) and should be of use in the developement of spectral techniques for the detection of this molecule.     

Tensor polarizabilities and lifetimes of levels of the configurations 4f 66s6p and 4f 55d6s2 in samarium I

Stark splittings of 7 levels of the configurations 4f ⁶6s6p and 4f ⁵5d6s² in Sm I were measured by quantum beat spectroscopy in pure electric fields, allowing the determination of tensor polarizabilities. Additionally, the lifetimes of 11 levels of these configurations were determined from time-resolved registration of the exponential decay. From these values the radial integrals I(6p,6s), I(6p,5d), and I(5d,4f) were derived by a parametric analysis. Theoretical values of tensor polarizabilities and lifetimes which were calculated using these radial integrals show good agreement with experimental data of various authors.     

Lifetime measurements in Gd II and Gd III using time-resolved laser spectroscopy

Natural radiative lifetimes of 20 levels (energy range between 29 000-35 000 cm^-1) in Gd II and 5 levels (energy range between 43 000-49 000 cm^-1) in Gd III have been measured using time-resolved laser-induced fluorescence in a laser-produced plasma. Received 17 July 2000 and Received in final form 13 October 2000     

Radiative lifetimes,branching ratios and absolute transition probabilities of atomic uranium by delayed photoionization measurements

Radiative lifetimes of ten even-parity energy levels of atomic uranium in the 15,500–19,000 cm^?1 region and branching ratios of six transitions originating either from ground level (⁵L ₆ ^o ) or from lowest metastable level (⁵K ₅ ^o ) at 620.32 cm^?1 are measured employing three-step delayed photoionization technique. The lifetimes of five energy levels and branching ratios of five transitions are measured for the first time. By combining the experimentally measured values of radiative lifetimes and branching ratios, we have determined the absolute transition probabilities of six transitions of uranium and compared with those previously reported in the literature.     

Lifetime measurements of metastable states in Fe+

The lifetime of two metastable levels in Fe+ has been measured by laser probing of a stored ion beam. In the dense spectrum of Fe+, the metastable levels a (6)S(5/2) and b (4)D(7/2) were selected and their lifetimes were determined to be 230 +/- 30 and 530 +/- 30 ms, respectively. The lifetimes are compared with previous theoretical results. Metastable lifetime measurements of Fe+ are of great importance for interpretation of spectra from astronomical objects. The present experiment opens for the possibilities to investigate lifetimes of metastable states in complex atomic ions, which have, so far, been unexplored.     

Theoretical calculation of energy levels and radiative lifetimes of Tl I

Considering the perturbation, the results of theoretical calculation of five Rydberg series energy levels 6s2ns^2S1/2 （n = 7 - 20）, 6s^2nd^2D3/2 （n = 6 - 20）, 6s^2nd^2D5/2 （n = 6 - 20）, 6s^2np^2P1/2^0 （n = 7- 20）, and 6s^2np^2P3/2^0 （n = 7-20） for Tl I are presented using the weakest bound electron potential model （WBEPM） theory. Furthermore, the radiative lifetimes of this five series are also calculated. The calculated values of energy levels and lifetimes are in good agreement with the experimental results.