Natural radiative lifetimes in the 5snd 1 D 2 series of SrI

Natural radiative lifetimes have been measured for the 5snd ¹ D ₂ series in SrI for the previously not measuredn=10, 11 and 12 states. The measurements connect earlier measurements in lower and higher states in this heavily perturbed series. The lifetimes were determined using pulsed laser excitation and time-resolved detection.     

Lifetime of the 4D 3/2 and 4D 5/2 metastable states in Sr II

Sr⁺ ions were confined in a r.f. quadrupole trap for times of the order of 30 min. The metastable 4D states were populated via laser excitation of the 5P states. The weak quadrupole transition rate into the 5S _1/2 ground state at 674 and 687 nm was deduced from observation of the exponential decay. At background pressures above 10^?7 mbar the radiative decay is dominated by collisional quenching. Extrapolation of the observed decay rate to zero background pressure yields the radiative lifetimes. At pressures around 10^?6 mbar fine structure mixing collisions between the 4D states have been observed, which lead to corrections of the extrapolated lifetimes. As the final result we obtain 395±38 ms for 4D _3/2 and 345±33 ms for 4D _5/2. These results are somewhat higher than theoretical predictions.     

Configuration interaction in the 6s n d 1 D 2 and 6s n s 1 S 0 states of Yb probed by lifetime measurements

Radiative lifetimes in the even parity 6s n d ¹ D ₂ (n=6?13) and 6s n s ¹ S ₀ (n=8?14) level series of neutral Yb have been measured. In contrast to a monotonicn*³ behaviour which is expected in the absence of configuration interaction a drastic decrease of the lifetime data was observed in the vicinity of multiply excited states. In addition, for certain levels a strong increase of the lifetime values has been found which may be ascribed to destructive interference due to configuration mixing which can also affect the branching ratios of the radiative decay of these levels.     

Radiative lifetimes and depopulation cross-sections of excited rubidium2 S and2 D states

The radiative lifetimes of excited rubidiumn ² S (n=8?13) andn ² D (n=6?11) states have been measured using the time resolved laser induced fluorescence method. The cross-sections for depopulation of the excited states in collisions with the ground-state Rb atoms have been determined. The influence of the blackbody radiation on the measured values is discussed.     

Natural radiative lifetimes in the2 S 1/2 and2 D 3/2, 5/2 sequences of neutral copper

Natural radiative lifetimes have been measured of the 3d ¹⁰ ns ² S _1/2 (n=6?10) and of the 3d ¹⁰ nd ² D _{3/2, 5/2} (n=5?9) sequences by using two step excitation of copper atoms in an atomic beam. The states investigated were populated by the light from two pulsed dye lasers pumped by the same Nd:YAG laser. The lifetimes of the² D sequence increase regularly with increasing principal quantum number. This is not the case for the² S series, because of configuration interaction in the² P series. In addition the lifetime of the 3d ¹⁰5p ² P _3/2 state has been measured together with its branching ratio.     

Spectroscopy of triatomic hydrogen

The visible emission spectra of H₃, D₂H, H₂D and D₃ were studied. Triatomic hydrogen molecules were produced by neutralization of fast ion beams in alkali vapors. In addition to the well-known 0-0 bands, weak vibrational bands of the electronic 3p ² A″ ₂ → 2s ² A′ ₁ transition of D₃ and D₂H were observed and analyzed. From the decay of the emission along the molecular beam lifetimes of excited states were obtained. For all observed states, 3p ² A″ ₂, 3s ² A′ ₁ and 3d, lifetimes strongly depend on the isotopic mixture. Many lifetimes measured were considerably shorter than ab initio predictions of the radiative lifetimes. Thus radiationless decay is important for all these excited states. Predissociation of the 3p ² A″ ₂ state increases with the rotational quantum number. Possible decay channels are discussed.     

Lifetimes and perturbations of the 3d9 4s(3D) 4p structure in the spectrum of copper I

Natural radiative lifetimes have been measured of the²P,²D,²F and⁴D_5/2 terms in the 3 d⁹ 4s(³D) 4p structure of copper I. A pulsed hollow cathode was used to generate 3d⁹ 4s^{2 2}D metastable atoms. From these metastable levels the states investigated were populated by a pulsed dye laser pumped by a Nd:YAG laser. A comparison with theoretical and experimental literature values is given.     

Lifetime measurements of the 3d 94s(1 D) 4p configuration of Cu I

The radiative lifetimes of the levels in the 3d ⁹4s(¹ D)4p configuration of Cu I are measured. The levels are excited from the metastable 3d ⁹4s ^{2 2} D _3/2,5/2 levels. The metastable Cu atoms are generated in a pulsed hollow cathode discharge. The levels investigated are populated with a 35-ps laser pulse at wavelengths around 220 nm. The laser induced fluorescence signal is detected. The lifetime of the 3d ⁹4s(³ D)4p ⁴ D _1/2 level is also determined by direct excitation from the ground state. A comparison with calculated literature values is given.     

Radiative and autoionization rates of the metastable 24 P J 0 states in lithiumlike neon

The delayed X-ray and electron emission from metastable states in fast, foil excited neon ions has been investigated. High resolution X-ray and electron spectroscopy at calibrated relative detection efficiencies was applied to determine fluorescence yields for the radiative decay of the (1s2s2p)⁴P _J ⁰ , J=1/2, 3/2, 5/2 states in NeVIII. Using measured total lifetimes corrected for cascading effects the forbidden radiative and autoionization rates were determined.     

Determination of radiative lifetimes in the 3snp 1 P 1 sequence of Mg I using time-resolved VUV laser spectroscopy

The radiative lifetimes of the states in the (n=5–8) 3snp ¹ P ₁ sequence of neutral magnesium were investigated using time-resolved laser-induced fluorescence. Excitation from the 3s ^{2 1} S ₀ ground state was performed using VUV radiation, which was produced by resonant sum-difference frequency mixing in a krypton gas cell. We find τ(n=5): 54(3) ns, τ(n=6): 140(10) ns, τ(n=7): 290(20) ns. τ(n=8): 475(40) ns. These results were found to be in fair agreement with a Multi Configuration Hartree-Fock (MCHF) calculation.     

A detailed consideration of resonance radiation trapping in the argon inductively coupled plasma

The extent and duration of trapping of argon resonance radiation (106.7 and 104.8 nm) in the ICP was calculated using a model incorporating line shape contributions from both Doppler and pressure broadening. The trap was found to be at the pressure-broadened limit, giving an escape factor of 7.9 × 10^?4 when excitation of the 4s states in the plasma annulus is assumed. Theoretical apparent radiative lifetimes τ_app for argon ³P₁ and ¹P₁ resonance states are calculated to be 8 and 1.9μs respectively. The quartet of 4s states, rapidly mixed by electron collisions, are presumed to share an overall apparent radiative lifetime τ_app = 1.6μs for the purpose of plasma modeling. Effects of this radiation trapping on the argon 4s atom density and on electron-ion recombination are discussed.     

Lifetimes of the 4s4p 3 P 1 and 4s3d 1 D 2 states of Ca I

The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ metastable states of Ca have been studied using the time-of-flight technique. Two kinds of observations were performed. First, the exponential decay of the fluorescence, using a (continuous) dc discharge for excitation and then the velocity distribution of the radiating atoms, using a pulsed discharge, were measured. From the combined results of these measurements the lifetimes were derived. The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ states of Ca are determined to be 0.57±0.03 ms and 1.5±0.4 ms, respectively.     

Lifetime measurements of highly excited Rydberg states of strontium I

Lifetimes of Rydberg states of the triplet-series 5s ns ³ S ₁ withn = 19–23, 35 and 5s nd ³ D ₃ withn = 18–20, 23–28 in the spectrum of neutral strontium have been determined. Observation of the exponential decay after excitation by a pulsed laser in a fast atomic beam and subsequent state-selective field ionization was employed. The lifetimes of the states of the³ S ₁-series show the expectedn*³ dependence on the effective principal quantum number, while the³ D ₃-series is disturbed by configuration mixing. Furthermore, state re-populations induced by black-body radiation have been observed.     

Calculations on transitions in singly- and doubly-excited C IV

Wavelengths for transitions in the quartet spectrum of C IV are calculated and compared with recent experimental measurements. Transition probabilities and radiative lifetimes are also predicted for several of the lowest 1s 2snl ⁴ L and 1s2pnl ⁴ L levels up toL=4. In addition, wavelengths and transition probabilities for some recently observed C IV doublet transitions to then=4 level are presented.     

Wavelengths and transition probabilities in the quartet spectrum of NV

Energies and structures of 1s2snl ⁴ L and 1s2pnl' ⁴ L core-excited levels in lithium-like NV are calculated. Wavelengths, transition probabilities and radiative lifetimes are reported and compared with available experimental data. It is suggested that the 1s2p4d ⁴ P ⁰,⁴ D ⁰ levels are nearly degenerate in NV and have not been resolved experimentally. Several new assignments for observed lines are proposed.     

Calculations of high lying energy resonances in the photoionization spectra of Ne+ using the screening constant by unit nuclear charge method

We report in this paper, energy resonances of the 2s²2p⁴ (¹D₂)ns,nd, 2s²2p⁴(¹S₀) ns,nd and 2s2p⁵ (³P₂)np series originating from both 2s²2p^{5 2}P_1/2 metastable and 2s²2p^{5 2}P_3/2 ground state of Ne⁺. Calculations are performed using the Screening Constant by Unit Nuclear Charge (SCUNC) method and high lying states up to n=75 are investigated. The results obtained in this work agree very well with Advanced Light Source experiments on Ne⁺ (Covington et al., 2002). The analysis of the present results is achieved by calculating the effective charge number in the framework of the SCUNC formalism and by evaluating the quantum defect from the standard quantum defect expansion formula. Both effective nuclear charge and quantum defect are almost constants up to n=75.     

Determination of radiative lifetimes in neutral nitrogen using short laser pulses from a distributed feedback dye laser

Radiative lifetimes were determined for two short-lived states in neutral nitrogen. Following photo-dissociation and two-photon excitation employing the same UV source, excitation to higher states was performed with a distributed feedback dye laser (DFDL). The lifetimes were found to be τ(2p ²4d ⁴ D _7/2)=17(3) ns and τ(2p ²5s ⁴ P _5/2)=22(3) ns.     

Analysis of the molecular bands of D2H and H2D at 5600 Å

Spectral simulation was used to analyze the molecular rovibrational bands of D₂H and H₂D at 5600 Å. These bands were previously measured by the ion beam neutralization method. They were assigned to the electronic 3p²B₁ ? 2s²A₁ and vibrational (ν - ν″) = (0, 0, 0,-0, 0, 0) transitions. Least squares fits to the experimental line-positions were made to determine the asymmetric rotator constants A, B and C for the 2s²A₁ and 3p²B₁ ν = 0 states of D₂H and H₂D, hitherto unknown. Lorentz line-profiles were assumed for the D₂H and H₂D rotational lines, whose widths are mainly governed by the lifetimes of the lower states. The bands at 5600 Å were simulated and the 2s²A₁ state lifetimes were estimated to be σ ≥ 0.5 ± 0.2 ps for D₂H and σ ≥ 0.4 ± 0.2 ps for H₂D. Vibrational constants of D₃ and D₂H in the 2s²A₁ states are determined from the positions of the 0-0 and 0-1 vibrational bands given in respective experimental spectra previously measured. For the first time the vibrational constants ω₁ and ω₂ of the 2s²A₁ state of H₂D were estimated from the positions of the 0-0 and 0-1 band maxima. These vibrational constants are compared with the corresponding vibrational constants of their ions.     

Vibrational radiative lifetimes in H2Se and HCS−

Vibrational dipole matrix elements and radiative transition probabilities for H₂Se and HCS⁻ have been evaluated from theoretical three-dimensional electric dipole moment and potential energy functions. The radiative lifetimes of the (v=1,J=0) levels of HCS⁻ have been calculated to be 3.5 ms (CH stretch), 172 ms (HCS bend) and 785 ms (CS stretch), and in H₂Se to be 122 ms (symmetric stretch), 1045 ms (bend) and 101 ms (asymmetric stretch). The lifetimes of higher vibrational states with no extensive mode-mixing decrease with increasing vibrational quantum number and vary in a mode-specific way.     

Radiative lifetime of the Te2 B0+u and A0+u states excited by a pulsed dye laser

A pulsed dye laser has been used to measure the radiative lifetimes and quenching rates of transitions of the B0⁺_u and A0⁺_u states of Te₂. The observed zero pressure lifetimes vary from 55 to 730 ns. The quenching rates vary from 0.9 × 10⁶ to 40 × 10⁶ s⁻¹ Torr⁻¹.