Measurement of L x-ray production cross sections by 60 keV photons and average L shell fluorescence yields of lanthanides

L x-ray production cross sections have been measured for lanthanides with 60 keV. The measured L x-ray production cross section values for the lanthanides are in good agreement with the theoretical ones evaluated using L _i subshell fluorescence yields ω_i, Coster-Kronig transition probabilities ? _ij based on the Relativistic-Hartree-Slater theory, K to L _i subshell vacancy transfer probabilities n _KLi, fractions of the ratiative width of the subshell F _ny and L _i subshell photoionisation cross section σ_Pi. The average L shell fluorescence yields ω_L have also been derived using the presently measured total L x-ray production cross section values and the theoretical K to L shell vacancy transfer probabilities. These results are compared with theoretically predicted values.     

Measurement of K shell radiative transition probabilities and K, L2 and L3 shell/subshell fluorescence yields of some elements in the atomic number range 30 ≤ Z ≤ 40

K shell radiative transition probabilities and K, L₂ and L₃ shell/subshell fluorescence yields were measured using the K_β/K_α intensity ratio for seven elements in the atomic number range 30≤Z≤40 (Zn, As, Se, Rb, Sr, Y and Zr). The targets were irradiated with γ photons of energy 59.5 keV from Am-241. The obtained values were compared with the theoretical values. It was observed that the present values agree with previous theoretical results. The L₂ and L₃ subshell fluorescence yields were the first measured for the present elements.     

Photoionization of the 2s, 2p and 3s subshells of Mg+

We present calculations of total and partial photoionisation cross sections for the 2s, 2p and 3s subshells of Mg⁺ from their ionisation thresholds up to a photon energy of 220 eV. Photoelectron angular distribution parameters are also calculated for the 2p subshell. Oscillator strengths are given for discrete structure, and calculated energy levels compared with experimental values. The significance of electron correlations and two electron excitation for this atomic ion is discussed.     

Measurement of L subshell fluorescence yields of some elements in the atomic range 75⩽Z⩽92 using photoionization

L subshell fluorescence yields (ω₁, ω₂ and ω₃) for the elements Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Th and U have been measured at the 123.6 keV γ-ray emission excitation energy from a ⁵⁷Co annular radioactive source (925 MBq) using a Si(Li) detector. The measured L subshell fluorescence yields were compared with the theoretical and semi-empirical values.     

Chemical effect on L X-ray fluorescence cross-sections of Hg,Pb and Bi compounds

Chemical effect on the photon induced L X-ray fluorescence cross-sections (σ_Lα, σ_Lβ and σ_Lγ) for Hg, Pb and Bi compounds were investigated. The samples were excited by gamma rays with energy 59.5 keV from ²⁴¹Am radioisotope source. L X-rays emitted by samples were counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. We observed chemical effect on the photon induced L X-ray fluorescence cross-sections (σ_Lα, σ_Lβ and σ_Lγ) for Hg, Pb and Bi compounds. Our values were compared with calculated theoretical values.     

Measurement of Cu K and Ag,In and Sn L X-ray production cross sections by low-energy positron impact

Cu K and Ag, In and Sn L X-ray production cross sections by positron impact have been determined experimentally in the energy range below 30 keV using an X-ray detector with thin Si(Li) crystals. These values have been compared with theoretical estimates derived using the binary encounter formalism. The values for Cu K and Ag L X-rays have also been compared with the results of theoretical calculations using the plane-wave Born approximation with Coulomb and relativistic corrections.     

L-shell ionization in Au by O5+-and Ni5+-ion impact

TheL X-ray production cross sections in gold by 60 to 72 MeV O⁵⁺ ions and 58 to 87 MeV Ni⁵⁺-ions have been measured. TheL-subshell ionization cross sections derived from these experimental results have been compared with the direct ionization theories viz. plane wave Born approximation (PWBA) theory and modified perturbed-stationary-state theory with energy loss, Coulomb deflection and relativistic effects (MECPSSR). A new procedure has been described to account for the change in the yield ratioLβ₁/Lβ_{2, 15} with energy, for Ni⁵⁺-ion impact on gold. TheL sub-shell ionization cross sections have been derived fromLβ₁,Lβ₄ andLβ_{2, 15} lines of theLβ group in addition to those calculated by the conventional Datz TRY3 technique usingLα,Lγ₁ andLγ_{2, 3} X-ray lines. From the shift in the energies of variousL X-ray lines and changes in their intensities, 3 and 5 spectator vacancies in theM- andN-shells in gold have been estimated with O⁵⁺-ion impact while 7, 20 and 4 to 6 spectator vacancies have been inferred in theM-,N-andO-shells respectively with Ni⁵⁺-ion impact in the energy range of the projectiles undertaken in the present studies.     

K X-ray satellites of uranium bombarded with 500 MeV neon

K X-ray satellite spectra produced during the bombardment of uranium with 500 MeV neon, have been investigated with a high resolution crystal spectrometer. The experimental results are compared with theoretical predictions for vacancy production computed in the semiclassical separate atom perturbation theory and corrected forL subshell coupling and electron transfer from targetL shell into projectileK shell. The agreement between theory and experiment is rather good. It turns out, that the reduction ofL vacancy production due toL subshell coupling is essentially compensated by theL electron transfer from target to projectile. The present work is an extension of a previous study of theK α₁ satellite spectra of tantalum bombarded with 403 MeV nitrogen.     

Measurements ofL-subshell fluorescence yields for light and medium heavy elements (28≤Z≤47)

We report on the first determination ofL-subshell fluorescence yields, ω_Li, for various elements with 28≤Z≤47. The method applied is based on the subshell ionization by relativistic electron impact with an electron energy ofE ₀=50 keV and the detection of characteristic X rays by means of a high resolution crystal spectrometer calibrated absolutely with respect to its transmission and reflectivity. The number of initialL vacancies and its subshell distribution as well as the normalized X-ray transition probabilities, the Coster-Kronig yields and theK-shell Auger transition rates are taken from theory. The results obtained for ω_Li yield values that are for all three subshells in agreement with the predictions of a widely used semi-empirical formula and for ω _L2 and ω _L3 also with theoretical calculations. The values of ω _L1, however, exceed the theory systematically.     

Partial oscillator strengths for the photoionization of N2O and CO2 (20–60 eV)

The photoelectron branching ratios and the partial oscillator strengths (cross sections) for photoionisation of the valence orbitals of N₂O and CO₂ have been obtained in the energy range 20–60 eV using the magic angle dipole (e, 2e) method. In addition to single electron ionization processes there is a large contribution from multiple electron transitions at higher energies in agreement with recent theoretical predictions. The photoionization efficiency and the dipole oscillator strenght for total photoabsorption have also been measured.     

Alignment of atoms following photoionisation: Cd+(4d −1 2 D 5/2,2 D 3/2) and Zn+(3d −1 2 D 3/2)

The linear polarisation of fluorescence radiation following the photoionisation in the 4d _5/2 and 4d _3/2 subshells of Cd and in the 3d _3/2 subshell of Zn has been measured in the energy range of primary photons from threshold up to about 40 eV. The experimental values of the linear polarisation found for the fluorescence radiation of Cd⁺(4d ^?1) ions are in essential agreement with theoretical results obtained by an RRPA calculation (Johnson et al.). For the case of Zn⁺(3d ^?1) on the other hand, no theoretical data are presently available. Using the experimental values of linear polarisation of fluorescence radiation the values of the alignment tensorA ₂₀ have been evaluated for the ions Cd⁺(4d ^{?1 2} D _5/2,² D _3/2) and Zn⁺(3d ^{?1 2} D _3/2).     

HeIα photoionisation cross-section determination of Br atoms

An extended electron modulation spectroscopy method is described which allows the accurate determination of photoionisation cross sections of transient species relative to those of precursor compounds. In this paper cross section at 584 Å for atomic and molecular bromine transitions from neutral ground to lowest ionic states have been measured relative to that of the HBr⁺ (X²Π_1/2,3/2)←HBr(X¹Σ⁺) ionisation. Using the cross section of this HBr transition as an absolute standard and with relative cross-section data for ionisations leading to the accessible excited ionic states of Br⁺ and Br⁺₂, absolute total angle-integrated cross sections for the valence shell ionisation process in Br⁺ and Br⁺₂ are presented.     

The influence of the electron wave function on the PtL I andL III ionization probabilities by 3.6 MeV he impact

For 3.6 MeV He impact theL _I andL _III subshell ionization probabilities of Pt have been measured. Due to relativistic effects in the electron wave functions, theL _I subshell ionization probabilityI _LI (b) is strongly enhanced at small impact parameters exceeding evenI _LIII (b) in nice agreement with the SCA theory.     

Mξ, Mαβ, Mγ and Mm X-ray production cross-sections for elements with 71⩽z⩽92 at 5.96 keV photon energy

The M_ξ, M_αβ, M_γ and M_m X-ray production (XRP) cross-sections have been measured for the elements with 71⩽Z⩽92 at 5.96 keV incident photon energy satisfying E_M1<E_inc<E_L3, where E_M1(L3) is the M₁(L₃) subshell binding energy. These XRP cross-sections have been calculated using photoionization cross-sections based on the relativistic Dirac–Hartree–Slater (RDHS) model with three sets of X-ray emission rates, fluorescence, Coster–Kronig and super Coster–Kronig yields based on (i) the non-relativistic Hartree–Slater (NRHS) potential model, (ii) the RDHS model and (iii) the relativistic Dirac–Fock (RDF) model. For the third set, the M_i (i=1–5) subshell fluorescence yields have been calculated using the RDF model-based X-ray emission rates and total widths reevaluated to incorporate the RDF model-based radiative widths. The measured cross-sections have been compared with the calculated values to check the applicability of the physical parameters based on different models.     

Resonant electron transfer andL-shell excitation at 3.6 MeV/u62Sm q+ → Xe collisions,q=34−52

For 3.6 MeV/u Sm ^q+ projectiles a hump in the projectile (L _l +L _α) x-ray emission cross section is seen as a function of charge stateq for highq with 46≦q≦52 (closed incomingL shell). This hump is attributed to the Resonant electron Transfer from the Xe target atom with simultaneous Excitation of anL ₃-shell electron to theM shell. The cross section for thisL ₃-shell RTE process has values up to 2·10^?19 cm², which is seen in single spectra already. To verify the existence of theL-shell RTE process for the studied collision system, extensive calculations have been carried out. Especially theL ₃-shell fluorescence yield for the radiative stabilization process in the highly-charged projectile has been considered. Our calculatedq-dependent cross sections for the RTE process support the given interpretation.     

Ground state correlations in H2 measured by the (e,2e) technique

The relative intensities for exciting the 1sσ_g, 2pσ_u, 2pπ_u, and 2sσ_g states of H₂ are measured in a 1200 eV noncoplanar symmetric (e,2e) experiment on H₂. Momentum distributions are obtained at separation energies corresponding to the various transitions. The ratio of transition probability to the excited states relative to the ground state is strongly dependent on the ion recoil momentum q, having a minimum value of approximately 2% at small q. The excited state cross sections are sensitive to electron correlation effects and the data are compared with calculated cross sections using a configuration interaction wavefunction for H₂.     

Energy and CKT dependence of proton induced L subshell X-ray intensity ratios in elements 57⩽Z⩽92

The dependence of L subshell X-ray intensity ratios on incident proton energy and the CK transitions has been investigated in elements 57⩽Z⩽92. The intensity ratio I(L_α)/I(L_l) neither shows variation with energy nor any dependence on the CK transitions. In general, the ratios I(L_α)/I(L_β) and I(L_α)/I(L_γ), first increase with incident proton energy, attain a maximum value, then start decreasing and attain an almost constant value after a particular energy (ranging from about 4.6 MeV for La to 5.8 MeV for U). A comparison has been made among the intensity ratios evaluated using three different sets of parameters. A maximum difference of about 18% has been observed among the different values.     

Nd,Yb, Au and UL-subshell ionization probabilities for 92 MeV Ar impact

The Nd, Yb, Au and UL-subshell X-ray emission probabilities as function of the impact parameter have been measured by X-ray—particle coincidence for 92 MeV Ar impact. The derivedL-subshell ionization probabilities show severe deviations from first order perturbation theory (SCA + corrections), although the totalL-shell ionization probabilities are still fairly well described by this approach. As is obvious from the data analysis, the discrepancy is due toL-substate coupling during the collision, which has a strong influence on the subshell ionization process, but is neglected in this theoretical approach. The observed influence of the multiple outer shell ionization on the measured data is also discussed.