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.     

Experimente mit Erdalkaliatomen in metastabilen Zuständen

An atomic beam source for atoms in metastable states is described. The source was used to produce metastable Ca and Sr atoms in the³ P _0,1,2 and¹ D ₂ and Mg atoms in the³ P _0,1,2 states. The population of these levels was high enough (about 30% of the atoms were in the³ P levels and 3% in the¹ D ₂ level) so that zero field level crossing experiments could be performed at highly excited levels which were populated by an optical excitation starting from the metastable states. The lifetime results obtained for Ca areτ(4s 4d ³ D ₁)=(1.21±0.07)·10^?8sec,τ(4s 4f¹ F ₃)=(2.84±0.23)· 10^?8sec, andτ(3d 4p ¹ F ₃)=(6.15±0.62)·10^?8 sec. The three lifetimes have been evaluated using theg _J values forLS-coupling. The quoted uncertainties include the errors by a possible deviation fromLS-coupling.     

Polarisierte Anregung der metastabilen 6s 5d-Terme im Ba I-Spektrum und Messung derg J-Faktoren

In an atomic beam experiment Ba-atoms were excited in the metastable levels of the 6s 5d-configuration by optical pumping and electron impact. The three states 6s 5d ¹ D ₂ and³ D _1,2 were populated by optical excitation of the 6s 6p ¹ P ₁- and³ P ₁-level resp., which decay partly into the metastable states. The¹ D ₂- and³ D ₃-level could be excited and aligned by impact of 50 eV-electrons. Radiofrequency transitions between Zeemansublevels were detected by resonance scattering of light and theg _J-values of the four 6s 5d-levels were measured:g _J(^1D ₂)=1.0032 (2),g _J(^3D ₁)=0.4986 (2),g _J(^3D ₂)=1.1638 (2) andg _J(^3D ₃)=1.3341 (2).     

Radiative decay and autoionization in the4 D-states of the 3d 94s5s configuration in CuI

The CuI 3d ⁹4s5s ⁴ D-states, which lie above the ionization limit, were populated by stepwise collisional and laser excitation. With respect to their total angular momentum, the⁴ D-states have completely different decay modes. Whereas the lifetimesτ(⁴ D _7/2)=8.2(4)·10^?9s andτ(⁴ D _1/2)=7.9(6)·10^?9 s are determinrd by radiative transitions and were measured by time-resolved spectroscopy, the lifetimesτ(⁴ D _5/2)=1.59(6)·10^?12s andτ(⁴ D _3/2)=1.28(5)·10^?12s are due to autoionization and were deduced from the widths of the excitation signals observed by ion detection.     

High precision measurements of the hyperfine structure of seven metastable atomic states of57Fe by laser-Rf double-resonance

The hyperfine structure of the metastable atomic states (3d ⁷4s)⁵ F _2,3,4,5 and (3d ⁷ 4s)³ F _2,3,4 of⁵⁷Fe has been measured using theABMR- LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). From these measurements the following hfs constantsA of the magnetic dipole interaction have been obtained (corrected for second order effects):A(⁵ F ₂)=55.994(7) MHzA(⁵ F ₃)=69.632(5) MHzA(⁵ F ₄)=78.435(4) MHzA(⁵ F ₅)=87.246(3) MHzA(³ F ₂)=143.328(4) MHzA(³ F ₃)=50.602(10) MHzA(³ F ₄)=13.456(5) MHz     

Hyperfine structure of the 8p 2 P 3/2 and 8p 2 P 1/2 levels of115In

The hyperfine structure of the 8p ² P _3/2 and² P _1/2 levels of¹¹⁵In was measured using high-resolution laser spectroscopy on a collimated indium atomic beam. Step-wise excitations from the metastable 5² P _3/2 state via the shortlived 6s ² S _1/2 state were employed. For the magnetic-dipole and electric-quadrupole interaction constantsa andb, respectively, the following results were obtained:a(8p ² P _3/2)=16.3 (3) MHz,b(8p ² P _3/2)=11 (3) MHz anda(8p ² P _1/2)=44.0 (5) MHz. The magnetic hyperfine structure is shown to be strongly influenced by core polarization. For the electric-quadrupole moment of¹¹⁵In the valueQ=0.79 (20) barn is deduced.     

Hyperfine-structure investigation in the 6s5d configuration of135Ba and137Ba

The hyperfine structure of the metastable states of the 6s5d configuration of¹³⁵Ba and¹³⁷Ba has been studied by the atomic-beam magnetic resonance (ABMR) method. The metastable barium states were populated in a plasma-discharge inside the atomic-beam oven. The atoms emerging from the ABMR-apparatus were detected by the use of a dyelaser. Compared to conventional methods this technique has the advantage of being state selective. The following magnetic dipole and electric quadrupole interaction constantsa andb have been obtained:¹³⁷Ba:a(³ D ₁)=?520.536 (3) MHzb(³ D ₁)=17.890 (3) MHza(³D₂=415.928 (3) MHzb(³D₂)=25.899 (13) MHza(³D₃)=456.559 (4) MHzb ³D₃=47.390 (16) MHz¹³⁵Ba:a ³ D ₁=?465.166 (4) MHzb(³D₁)=11.642 (4) MHza(³D₂)=371.736(4) MHzb ³ D ₂=16.745 (14) MHza(³D₃)=408.038 (6) MHzb(³D₃)=30.801 (24) MHz Using these constants and the earlier known ones for the¹ D ₂ state the hyperfine structure for the 6s5d configuration has been analyzed with an effective hyperfine hamiltonian. Hyperfine parameters obtained from the analysis have been compared with theoretical values calculated with relativistic self-consistent-field (SCF) wavefunctions. The quadrupole moments have been evaluated with the following result Q(¹³⁵Ba) =0.20(3)b and Q(¹³⁷Ba) = 0.34(4)b uncorrected for the quadrupole shielding.     

Untersuchungen zum Stark-Effekt metastabiler Terme im Ba I-Spektrum durch Nachweis von Hochfrequenzübergängen

By detection of r.f.-transitions between Zeeman-sublevels the Zeeman-splitting of the metastable 6s 5d-levels and of the 6s 6p³ P ₁-level of the even Ba-isotopes was investigated under the influence of an electric field in addition to a magnetic field. From the measurements the following tensor polarizabilities were deduced: α_ten(³D₃)=?29(5) kHz/(kV/cm)², α_ten(³ D ₂)=?13(3) kHz/(kV/cm)², α_ten(³D₁)=?10(2) kHz/(kV/cm)², α_ten(¹ D ₂)=?16(3) kHz/(kV/cm)². No effect due to electric fields up to 50 kV/cm was observed in the Zeeman-splitting of the 6s 6p ³ P ₁-level. Therefore the tensor polarizability of the 6s 6p³P₁-level must be much smaller than those of the 6s 5d-levels. The results will be discussed by considering the oscillator strengths both of the infrared transitions between the two multiplets 6s 5d ³ D and 6s 6p ³ P and of transitions to other low lying levels.     

Lifetimes and oscillator strengths in the triplet system of ZnI

Selective laser excitation was used to measure the radiative lifetimes of the ZnI triplet states 4sns ³ S ₁(n=5–7) and 4snd ³ D ₃,³ D ₂ and³ D ₁(n=4–6). These states were excited from the metastable 4s4p ³ P states, which were collisionally populated in an atomic beam. The values are compared with the results of other experimental methods (beam-foil, pulsed electron excitation, Hanle effect) and with theoretical calculations. The corresponding oscillator strengths are discussed with respect to the astrophysical determination of the Zn photospheric abundance.     

Experimentally determined transition probabilities of the systems 6p2→6p6d, 6p7s, 6p8s of neutral lead

Branching ratio measurements have been performed for all of the observed transitions from eight levels in neutral lead (6p²→6p6d, 6p²→ 6p7s, 6p²→6p8s) excited in a hollow cathode discharge in the 200–730 nm spectral range. From the relative emission intensity data, a set of absolute transition probabilities is derived for 28 lines, including lines for which transition probabilities have not been previously published. The absolute scales are obtained by averaging the measured lifetimes of the ³P⁰_1,2, ¹P_1⁰(6p7s), ³F^0_2,3, ³D^0_1,2(6p6d) levels.     

Laser-rf double-resonance hyperfine structure measurements of the metastable 3d 4s 1 D 2 state of43Ca

The hyperfine structure of the (3(d 4s)¹ D ₂metastable state of⁴³Ca has been measured using theABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence). The measurements yielded for the magnetic dipole and electric quadrupole constantsA=?17.650(2) MHz andB=?4.642(12) MHz, respectively. From the measuredB factor the spectroscopic electric quadrupole moment (uncorrected for shielding effects) has been calculated to beQ(⁴³Ca)=?0.062(12) barn. In addition, isotope shifts in the lines (3d 4s)¹ D ₂(3d 4p)¹ F ₃ ⁰ and (3d 4s)¹ D ₂(4s 5p)¹ p ₁ ⁰ for the stable calcium isotopes have been obtained by high resolution laser spectroscopy.     

Level crossing investigation of the 6p 2 P 3/2 and 7p 2 P 3/2 levels of Cs133, Cs135, and Cs137

The level crossing method has been used for the investigation of the hyperfine structure of the 6p²P_3/2 and 7p²P_3/2 levels of the isotopes Cs¹³³, Cs¹³⁵, and Cs¹³⁷. For the hyperfine coupling constants a and b and for the lifetimes Τ we find: a(6p Cs¹³³)=50.72(3) g_J/?1.345, b(6p Cs¹³³)=?0.38(18) g_J/?1.345 a(7p Cs¹³³)=16.610(6) g_J/?1.3349, b(7p Cs¹³³)=?0.15(3) g_J/?1.3349 a(6p Cs¹³⁵)=53.64(4) g_J/?1.345, b(6p Cs¹³⁵)=7.41(32) g_J/?1.345 a(7p Cs¹³⁵)=17.570(6) g_J/?1.3349, b(7p Cs¹³⁵)=2.35(7) g_J/?1.3349 a(6p Cs¹³⁷)=55.80(4) g_J/?1.345, b(6p Cs¹³⁷)=7.54(20) g_J/?1.345 a(7p Cs¹³⁷)=18.274(6) g_J/?1.3349, b(7p Cs¹³⁷)=2.37(4) g_J/?1.3349 (MHz), Τ(6p²P_3/2)=29.7(2) ?1.345/g_J ns, Τ(7p²P_3/2)=135(1) ?1.3349_Jns. From a comparison with double resonance results the g_J factor of the 7p²P_3/2 level was deduced: g_J(7p²P_3/2=?1.3349(10). Level crossing measurements in the 8p²P_3/2 state of Cs¹³³ give for the g_J factor and the lifetime the following results: g_J(8p²P_3/2)=?1.3353(14), Τ(8p²P_3/2)=310(15) ns. Using recently calculated relativistic correction factors and applying corrections for core polarization and the Sternheimer effect, we obtain for the quadrupole moments: Q(Cs¹³³)=?0.0030 b, Q(Cs¹³⁵)=+0.052 b, Q(Cs¹³⁷)=+0.052 b.     

Lifetime measurements in the triplet system of Mg I

In an atomic beam the metastable 3s3p ³ P-states of Mg I were populated by electron impact. A pulsed tunable dye laser was used to excite the metastable atoms to the 3snd³ D-(n=3–7) and to the 3sns³ S ₁-states (n=4and 6). Observing the time dependence of the reemitted resonance light the lifetimes of these states were measured.     

Lebensdauer- und Hyperfeinstrukturmessungen an einigen angeregten Zuständen der Konfiguration 4d 9 5p im Pd I-Spektrum mit der Level-crossing-Methode

Lifetimes and hfs coupling constants of some excited states of the 4d ⁹ 5p configuration of Pd I have been determined in a level crossing experiment by observing the field dependence of the polarization of the fluorescence radiation in a magnetic field. From the halfwidths of the measured zero field level crossing signals one obtains the mean lifetimes of the following fine structure states:τ(³P ₁ ⁰ )=(7.46±0.32)nsec;τ(³ P ₂ ⁰ )=(6.9±0.76)nsecτ(³P ₁ ⁰ )=(4.99±0.35)nsec;τ(³ D ₁ ⁰ )=(4.89±0.40)nsecτ((³D ₃ ⁰ )=(6.99±0.49)nsec;τ(³ F ₄ ⁰ )=(7.09±0.46)nsec.Δm=2 crossing signals were detected in the³ P ₁ ⁰ ,³D ₃ ⁰ and³F ₄ ⁰ -states of the odd isotope¹⁰⁵Pd. A detailed analysis of the experimental curves yields the hfs coupling constantsA andB of these states:A(³P ₁ ⁰ )=?(133±2) Mc/sec;B(³ P ₁ ⁰ )=(140±30) Mc/secA(³D ₃ ⁰ )=?(120±10) Mc/sec;B(³ D ₃ ⁰ )=?(660±100) Mc/secA(³F ₄ ⁰ )=?(87±2) Mc/sec;B(³ F ₄ ⁰ )=?(330±30) Mc/sec. A theoretical calculation of the hfs constants is given on the basis of reduced matrix elements. Within the limit of the errors these values agree with the experimental ones. The nuclear electric quadrupole moment deduced from the measuredB values isQ (¹⁰⁵Pd)=(0.8±0.3)·10^?24 cm² (without corrections).     

Lifetime measurement of the (5d6p)3D3 state of barium by dye-laser spectroscopy

We have measured the radiative lifetime of the (5d6p)³D₃ state of barium by Hanle effect. This state was populated by cw dye laser excitation of an atomic beam of Ba in the metastable (5d6s)³D₃ state. The metastable state was populated by a dc discharge. With dye laser excitation, the shape of the Hanle effect curve is strongly modified due to optical pumping of the metastable state. A brief discussion of the expected and observed signal shapes is given. The radiative lifetime of the (5d6p)³D₃ state is measured to be τ = 10.2 ± 1.5 ns.     

Solution of Faddeev-type equations in the problem of two coulomb centers

The hyperfine structure of the 7p ² P _1/2,3/2 levels of¹¹⁵In and the 5p ² P _1/2 level of²⁷Al has been measured using high-resolution laser spectroscopy on atomic beams. For the magnetic-dipole and electric-quadrupole interaction constants,a andb, the following values were obtained;a(7p ² P _1/2)=90.7(10) MHz,a(7p ² P _3/2)=32.3(2) MHz andb(7p ² P _3/2)=24.5(1.5) MHz for¹¹⁵In anda(5p ² P _1/2)=20(2) MHz for²⁷Al. Many-body calculations on² P states in aluminum, gallium and indium have also been performed.     

Radiative lifetime measurements of odd-parity high-excited levels of Sn I by time-resolved laser spectroscopy

Natural radiative lifetimes of five higher-lying odd-parity levels 5p7s ³P₁^o, 5p5d ¹P₁^o, 5p6d ³F₂^o, ³D₁^o and ³F₃^o in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of even-parity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.     

Precision measurement of theg J factors of metastable atomic states of88Sr and138Ba using the atomic beam magnetic resonance method

Theg _J factors of the metastable states³ P ₂ of⁸⁸Sr and³ D ₁,³ D ₂,³ D ₃, and¹ D ₂ of¹³⁸Ba have been measured using the atomic-beam magnetic resonance method. The metastable states were populated by an electric discharge within the atomic-beam source. From the measurements of rf transitions between the Zeeman levels (m _J =+1)?(m _J =?1) we obtained:⁸⁸Sr:g _J (³ P ₂) =1.501124(10)¹³⁸Ba:g _J (³ D ₃)=1.3340823 (10)g _J (³ D′₂)=1.1637406(11)g _J (³ D ₁)=0.4985751(13)g _J (¹ D′₂)=1.003 1449(10). The relativistic and diamagnetic corrections for theg _J factor of the³ P ₂ state of Sr have been calculated. With these and the Schwinger correction included we getg _J (³ P ₂)=1.501119(12).     

Low pressure broadening and shift of the 2p 53p-2p 56s neon spectral lines

Natural radiative lifetimes in the perturbed 6s n s ¹ D ₂ (n=12?30) sequence of barium have been measured using the PUMOLS (PUlse-MOdulated Laser Spectroscopy) method, which incorporates pulse-modulation of a CW dye-laser beam and delayed coincidence techniques. Principal perturbers are the 5d 7d ³ F ₂ and¹ D ₂ states. Lifetimes were also measured for these shortlived valence states, which through configuration mixing cause drastic decreases in lifetime values in the region of perturbation of the 6s n d ¹ D ₂ sequence. Two-step laser excitation from the ground 6s ^{2 1} S ₀ state via the 6s 6p ¹ P ₁ state was employed. Special care was taken to determine the influence of black-body radiation transitions on the measured lifetimes.     

Doppelresonanzuntersuchung des Einflusses eines elektrischen Feldes auf die Zeeman-Aufspaltung des 5s 5p 3P1-Terms im SrI-Spektrum

Under the simultaneous action of external electric and magnetic fields the 5s 5p ³ P ₁-level of the even Sr-isotopes splits into three non-equidistant Zeeman-sublevels. In an atomic beam experiment the spacings between the sublevels were investigated by the double resonance method at a magnetic field strength of ca. 22 Oe and at electric field strengths up to ca. 17 kV/cm. From the r.f.-resonance signals the tensor polarizability of the 5s 5p ³ P ₁-level was deduced to be α_ten(³ P ₁)=6.1(8) kHz/(kV/cm)². This value may be used to get an estimate of the oscillator strength of the infrared transitions between the multiplets 5s 5p ³P and 5s 4d ³ D. Taking into account oscillator strengths of electric dipole transitions to other low lying levels one obtainsf(³ P→³ D)≈0.09.