Lifetimes and transition probabilities of Ar(II)

Radiative lifetimes of 16 levels belonging to the 3p⁴4p configuration of Ar(II) have been measured by using the delayed-coincidence method. Relative transition probabilities for 87 lines arising from these levels have been determined from emission line-intensity measurements. By using the corresponding experimental lifetimes, the relative transition probabilities were put on an absolute scale. Our experimental results are compared with experimental and theoretical data given by other authors and with our calculations in LS coupling.     

Feeding and lifetimes of yrast levels in Hf nuclei

Feeding intensities and times, as well as lifetimes of yrast levels in doubly even ^{166, 168, 170}Hf nuclei have been measured. The reactions ^{122, 124}Sn(^{48, 50}Ti, 4n)^166–170₇₂Hf have been investigated using the recoil-distance Doppler-shift method. The lifetimes, and hence the B(E2) values measured, show the same trends of rather small deviations from the rigid rotor as in the known ₆₈Er and ₇₀Yb cases. In addition to the fast feeding component, showing behaviour rather similar to that of the Yb nuclei, another type of slow feeding, related to the low spin yrast levels, is observed.     

Experimental natural lifetime determination of the Ar(II) lower laser levels

The natural lifetimes of the (³P)4s²P_3/2,1/2 levels of the Ar(II) spectrum have been determined from the natural broadening of argon lines, measured with a Fabry—Pérot interferometer. The natural broadening was determined from the lines with wavelengths of 4880 and 4965 Å by comparing them with the lines at 4806 and 5009 Å having negligible natural broadening. The natural lifetime of the 4s²P_3/2 level appeared to be τ = 0.19 (±6%) ns and of the 4s²P_1/2 level τ = 0.18 (±15%) ns. These values are about 1.5 to 2 times as small as those determined by other authors either experimentally by using a Fabry—Pérot interferometer by the method of Ballik, or calculated using intermediate coupling.The differences between the two experimental methods are discussed.     

Lifetime of levels belonging to the 3p54p configuration of Ar(I)

The lifetimes of nine levels of Ar(I) belonging to the 3p⁵4p configuration have been measured by the delayed coincidence method, with errors in the range from 4 to 7%. The results are compared with other experimental values and with theoretical calculations using jK coupling and intermediate coupling. From cascade components of the 4p levels, decay lifetime values for some levels belonging to the 3p⁵3d and 3p⁵5s configurations have been inferred.     

Lifetime measurement in the α system (C3Δ3-X3Δ3) of TiO

The radiative lifetimes of two rotational levels of the v′ = 2 level of the C³Δ₃ state of TiO have been measured using laser-induced fluorescence and delayed coincidence counting. Individual rotational levels are excited and observed. The measured lifetimes are τ_{J = 17} = 28.21 + 0.15 nsec and τ_{J = 87} = 29.74 ± 0.86 nsec. Argon-TiO collision cross sections have been determined for the two rotational levels and are found to differ by 30%.     

Lifetime measurements in166Er

The lifetimes of five states in the ground band, from spin 6⁺ up to spin 14⁺, and of all even states in the gamma band up to spin 12⁺, have been measured in¹⁶⁶Er using the recoil distance method. The reduced electric quadrupole transition probabilities have been determined from the measured lifetimes using previously measured branching ratios, and the mixing between the ground band and theγ-band has been studied. The transitional electric quadrupole moments for the ground band and theγ-band have been deduced and are discussed.     

Lebensdauern und Oszillatorstärken im Sr I- und Ca I-Spektrum

Radiative lifetimes of some highly excited levels in Sr I were measured by zero-field level crossing technique. These levels have been populated using optical excitation starting from the metastable 4d 5s ¹ D ₂ or 5s5p ³ P _2,1,0 states. The high population of these metastable levels necessary for the experiments was obtained by a discharge in the pure Sr vapour burning in the atomic beam oven. The following lifetimes have been determined (in units of 10^?8 sec):τ(5s 6s³ S ₁)=1.09±0.11,τ(5s 5d ³D₁)=1.67±0.10,τ(5s4f¹ F ₃)=3.43±0.28,τ(4d5p ¹ D ₂)=2.19±0.16,τ(5p ^{2 3}P₁)=0.88±0.12,τ(5p ^{2 3} P ₂)=0.78 _?0.10 ^+0.26 . These results are compared with lifetimes derived from oscillator strengths given in the literature, and the reliability of different oscillator strengths tables is discussed. A corresponding discussion is given for radiative lifetimes of some levels in Ca I published previously. Good agreement with data derived from arc emission oscillator strengths has been found. Ca lifetimes are fairly well consistent with oscillator strengths calculated with semiempirical scaled Thomas-Fermi-wave functions.     

Lifetime measurement of some excited states belonging to the 3p<Superscript>4</Superscript>nd (n=4–6) configuration of ArII

The radiative lifetimes of eight levels belonging to the 3p⁴nd (n=4–6) configuration of ArII have been measured using 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.      

Durees de vie des niveaux 1D2 ET 1S0 du magnesium

Radiative lifetimes of the excited n¹S₀ (n = 4, 5) and n¹D₂ (n = 3, 4) states in magnesium have been measured by time resolved fluorescence technique using two photon excitation.     

Radiative lifetimes of some excited CoI states

The lifetimes of atomic CoI states have been determined using the delayed coincidence technique. A tunable dye laser pumped by a nitrogen laser was employed for the excitation of cobalt atoms in an atomic beam. The lifetimes were derived from the time dependent fluorescence intensity of the observed lines after the excitation. For the measurement of the lifetimes of thee ⁴ F _9/2,f ⁴ F ^9/2 andf ⁴ F _7/2 levels a two step excitation was applied. In case of overlapping measurement we find our results to be in good agreement with those reported by Becker [1].     

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.     

A test of the absolute Ni(I) gf-value scale by using mean lives of selected levels for the configurations 3d84s4p and 3d94p

Lifetimes for 11 levels of the configurations 3d⁸4s4p and 3d⁹4p in Ni (I) have been measured by the delayed coincidence method, following selective dye-laser excitation in a wavelength range between 299 and 338 nm. The results are compared with earlier laser excitation and Hanle effect lifetime measurements and with lifetimes derived from the gf-values of Huber and Sandeman. Comparisons with the results of Huber and Sandeman show consistently excellent agreement.     

Radiative lifetimes and collisional quenching cross sections of selectively excited vibrational states of the B 2p1Σu+ state of H2

Radiative lifetimes between 0.54 ns and 0.69 ns have been measured for the vibrational levels υ′ = 0...4 of the B 2p¹Σ_u⁺ state of H₂ after selective excitation by synchroton radiation. Quenching by collisions with H₂ ground state molecules has been observed with cross sections of 5 × 10^-15 cm².     

Electromagnetic transitions in the ground-state rotational band of159Tb

The ground-state band of¹⁵⁹Tb has been Coulomb excited up to spin 23/2 by 151-MeV⁴⁰Ar ions. The lifetimes of the 9/2 to 23/2 levels have been determined by combining results obtained with the RD and DSA methods, theE2/M1 mixing ratios for ΔI=1 transitions have been measured using angular correlation techniques and the branching ratios for the levels up to spin 17/2 have been determined. The energies of the levels and the reducedM1 andE2 transition probabilities for their decay have been compared with the predictions of the rotational model, without and with ΔK=1 admixtures. No satisfactory agreement could be achieved for all available experimental data simultaneously.     

DSAM lifetime measurements in 26Mg with high-velocity recoils

Mean lifetimes of eight levels in ²⁶Mg have been measured using the ⁴He(²³Na, p)²⁶Mg inverse reaction. The lifetimes, determined by fitting Doppler-broadened line shapes observed at 0° to the beam, are (E_x in MeV, J^πτ in ps): 1.809, 2⁺, 0.653 ± 0.039; 2.938, 2⁺, 0.204 ± 0.012; 3.941, 3⁺, 1.020 ± 0.126; 4.318, 4⁺, 0.392 ± 0.023; 4.332, 2⁺, 0.029 ± 0.004; 4.834, 2⁺, 0.041 ± 0.008; 4.900, 4⁺ 0.042 ± 0.008; 5.291, 2⁺, < 0.015. The lifetime for the 4.900 MeV, 4⁺ level, combined with accurate branching ratios for its decay to the 1.809, 2⁺ level, indicates that it is the 4⁺ member of the ground-state rotational band.     

Study of Three-Quasiparticle Band in 83 Kr

Excited states of ⁸³Kr, populated in the ⁷⁶Ge(¹¹B, 3npγ) reaction at a beam energy of 50 MeV, have been studied. The ΔI?=?1 band, built upon the 2,510.0 keV state, has been observed up to 5,639.4 keV with spin (27/2^???). Mean lifetimes have been measured up to spin 23/2^?? in ΔI?=?1 band using the Doppler shift attenuation method. The B(M1) rates derived from the measured lifetimes decrease smoothly with spin indicating that the angular momentum belonging to this band are generated by the shears mechanism.     

Helium and argon line broadening in the ν2 band of CH4

The spectra of the gaseous mixtures CH₄-He and CH₄-Ar were obtained in the spectral region 1400-1750 cm⁻¹ with a resolution up to 0.003 cm⁻¹. Helium and argon pressure broadenings for the vibration-rotation lines of the ν₂ band of CH₄ have been estimated at room temperature for some lines in the P, Q, and R branches. These values were also calculated using the theoretical approach developed by Robert and Bonamy, extended to the case of tetrahedral molecules. The helium data have been found to be in a satisfactory agreement whereas a divergence of calculated and measured broadening coefficients has been evidenced in the case of argon. Simulations of the ν₂ band shapes of methane perturbed by helium have also been performed.     

Experimental lifetime of some level belonging to the 5p46d configuration of XeII

Lifetimes of eight levels belonging to the 5p⁴6d configuration of singly ionized xenon have been measured by high frequency deflection technique with a delayed coincidence single photon counting arrangement. The results have been compared with other experimental and theoretical values. The lifetimes of the 6d ²F_3/2 and 6d ⁴F_3/2 levels have been measured for the first time.     

DSA lifetime measurements in21Ne at high recoil velocity

States in²¹Ne up to 5 MeV excitation energy have been populated using the inverted reaction²H(²⁰Ne,pγ). The Doppler shift attenuation (DSA) analysis of thepγ coincidence spectra taken in a Ge(Li) detector at 45° and 135° and an annular silicon surface barrier detector near 0° yielded the lifetimes of 8 states in²¹Ne. Due to the large recoil ofπ _i/c～ 4% three new lifetimes were determined for the short lived levels at 2.80, 4.68 and 4.73 MeV, namely 10±4 fs, 16±4 fs and 10±4 fs, respectively. The results are compared with rotational and shell model calculations.     

Radiative lifetime of NaH A1Σ+ in a high frequency discharge

The radiative lifetimes of NaH, A¹Σ⁺, excited states have been measured by pulsed dye laser excitation. The hydride is obtained by h.f. discharge in hydrogen and metal vapor, at a total pressure less than 10^?1 Torr. The measured lifetimes are: (24.0 ± 3.0) ns for v′ = 3, J′ = 8; (28.3 ± 3.0) ns for v′ = 4, J′ = 11; (27.1 ± 3.0) ns for v′ = 5, J′ = 16.