Coster-Kronig Transition Probabilities Research Articles

An investigation of theL 2-L 3 Coster-Kronig transition probability for 63?Z?96

The total transition probabilityf 23 for theL 2-L 3 Coster-Kronig transition probability atZ=80, 81, 82, and 92 was measured withL α x-ray coincidences between high resolution Si(Li) and Ge(HP) x-ray detectors and a dual-parameter multichannel coincidence system. TheL α gating technique for observing theK x-ray coincidence spectrum was carefully checked and found to be equivalent to the method of observing theL x-ray spectrum with $$K_{\alpha _{1,2} } $$ gates, when proper corrections are applied. The values off 23 found are 0.123±0.012, 0.109±0.011, 0.105±0.011, and 0.146±0.018 atZ=80, 81, 82, and 92, respectively. These values, together with all previously published values in the region 57≦Z≦96, are critically evaluated and a group of “best values” selected for comparison with theory. The agreement is quite good in the region 63≦Z≦83. The independentparticle model employing a Green-Sellin-Zachor potential used by Chen and Crasemann predicts values off 23 which are too large compared with experiment in the high-Z region, whereas the theoretical predictions of McGuire using an approximate Herman-Skilman potential are too low. However, the screened nonrelativistic hydrogenic results of Chen, Crasemann, and Kostroun are in satisfactory agreement with the experiments. The experimental result atZ=92 indicates that theL 2-L 3 M 4 transition is at or below threshold and contributes little or no intensity to the value of f23.

Comparison of techniques for the determination of theL2−L3XCoster-Kronig transition probability

The value of the Coster-Kronig transition probability for $Z=73$ has been determined by eight variations of the $K\ensuremath{-}L$ x-ray coincidence technique. The effect of a correction for unwanted $L\ensuremath{\eta}\ensuremath{-}K{\ensuremath{\alpha}}_{2}$ coincidence events in the $L\ensuremath{\alpha}\ensuremath{-}K$ coincidence spectrum is discussed. The value reported for the Coster-Kronig transition probability at $Z=73$, ${f}_{23}=0.153\ifmmode\pm\else\textpm\fi{}0.002$, is a weighted average of measurements not involving this correction. This value is in excellent agreement with previous measurements but deviates significantly from theoretical predictions.

Experimental determination of theL2−L3XCoster-Kronig transition probability in europium, plutonium, and curium

The ${L}_{2}\ensuremath{-}{L}_{3}X$ Coster-Kronig transition probability for $Z=63, 94, \mathrm{and} 96$ has been measured by the $L$-x-ray---$K$-x-ray coincidence technique. The value measured in $_{63}\mathrm{Eu}$ was corrected for the presence of an unresolved $L\ensuremath{\eta}$ x-ray component in the $L\ensuremath{\alpha}$ x-ray group. The values reported are for $_{63}\mathrm{Eu}$, ${f}_{23}=0.172\ifmmode\pm\else\textpm\fi{}0.015$, for $_{94}\mathrm{Pu}$, ${f}_{23}=0.233\ifmmode\pm\else\textpm\fi{}0.015$, and for $_{96}\mathrm{Cm}$, ${f}_{23}=0.226\ifmmode\pm\else\textpm\fi{}0.017$.

L Subshell Fluorescence Yields and Coster–Kronig Transition Rates at Z = 88 and 94

The L2 and L3 subshell fluorescence yields, ω2 and ω3, and the Coster–Kronig transition probability f23 in 88Ra and 94Pu have been deduced from conversion electron L X-ray coincidence measurements. The Chalk River [Formula: see text]-spectrometer was used to select the conversion electrons. X rays were detected in a Si(Li) counter which was calibrated for absolute X-ray detection efficiency. The results are as follows: [Formula: see text]

L2−L3XCoster-Kronig Transition Probability atZ=82

The probability for Coster-Kronig transfer of vacancies from the ${L}_{2}$ to the ${L}_{3}$ subshell of Pb is measured by observing the $K$ x-ray spectrum in coincidence with $L\ensuremath{\alpha}$ x rays in the electron-capture decay of ${\mathrm{Bi}}^{207}$. The intensity of the $K{\ensuremath{\alpha}}_{2}$ component of the coincident spectrum is a measure of the ${L}_{2}\ensuremath{-}{L}_{3}X$ Coster-Kronig transition probability. A value of 0.156 \ifmmode\pm\else\textpm\fi{} 0.010 is obtained for ${f}_{23}$.

TheoreticalL2- andL3-Subshell Fluorescence Yields andL2−L3XCoster-Kronig Transition Probabilities

${L}_{2}$-subshell fluorescence yields ${\ensuremath{\omega}}_{2}$ and ${L}_{2}\ensuremath{-}{L}_{3}X$ Coster-Kronig transition probabilities ${f}_{23}$ have been calculated for 21 elements with atomic numbers $26<~Z<~93$, and ${L}_{3}$ fluorescence yields ${\ensuremath{\omega}}_{3}$ were computed for 14 atoms with $26<~Z<~85$. Radiationless transition probabilities were calculated in $j\ensuremath{-}j$ coupling from screened nonrelativistic hydrogenic wave functions. All contributing Auger matrix elements including states through $4{f}_{\frac{7}{2}}$ were included. The theoretical Auger widths were combined with Scofield's x-ray emission rates to derive fluorescence yields. Results from ${\ensuremath{\omega}}_{2}$ and ${\ensuremath{\omega}}_{3}$ are in very good agreement with experiment. The calculated Coster-Kronig transition probabilities are close to those derived by McGuire from a self-consistent-field potential. However, the theoretical ${f}_{23}$ curves differ by \ensuremath{\sim}35% from measured values of ${f}_{23}$. No explanation for this discrepancy has been found.

LEED and Auger investigations of Cu (111) surface

After ultrahigh vacuum bake-out, electropolished Cu (111) surfaces were shown by Auger analysis to be contaminated by C, N, O, S and Cl. Other than C and S, which were contained in the bulk, the impurities were introduced by surface preparation; but all were easily removed by light Ar ion bombardment. Heating to ≈ 750°C caused diffusion of C and S from the bulk to the extent that a clear diffraction pattern corresponding to a √7 × √7 structure was produced by S on the surface. At ≈ b 900°C evaporation of Cu occurred to an observable degree, and S and C could no longer be detected on the surface. Auger analysis of clean Cu surfaces showed many details of the LMM and MMM types of transitions. Kinetic energies of all observed Auger electrons were in excellent agreement with calculated values. Also, the ≈ 62 eV MMM peak was resolved into two components related to the small differences in the M 2 and M 3 energy levels. The LMM transitions were classified according to their intensities, which could be rationalized on the basis of Coster-Kronig transitions and transition probabilities, as L 3MM > L 2MM > L 1MM.

Relativistic Study ofL1L2M4,5Coster-Kronig Transitions

A relativistic expression for ${L}_{1}{L}_{2}{M}_{4,5}$ Coster-Kronig transition probabilities has been obtained by using the solutions of the Biedenharn symmetric Dirac-Coulomb Hamiltonian. The interaction matrix element yields the well-known nonrelativistic result in the appropriate limit. Numerical results for atoms having $Z$ values between 32 and 41 are compared with earlier calculations. Relativistic effects are shown to be sufficiently pronounced as not to be critically affected by the choice of a screening parameter. The transition probability at the cutoff point is appreciably greater than earlier nonrelativistic values.

Electron-Capture Decay ofBi207:L-Subshell Fluorescence Yields and Coster-Kronig Transition Probabilities of Pb

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L2−L3NCoster-Kronig Transition Probabilities andL-Subshell Fluorescence Yields of Hg and Ta

The probability for the radiationless transfer of ${L}_{2}$ vacancies to the ${L}_{3}$ subshells of Hg and Ta has been measured directly, by observing the spectra of $L$ x rays from ${\mathrm{Tl}}^{204}$ and ${\mathrm{W}}^{181}$ in coincidence with ${K}_{{\ensuremath{\alpha}}_{2}}$ x rays. The ${L}_{\ensuremath{\alpha}}$ component of the coincident spectrum provides a measure of the ${L}_{2}\ensuremath{-}{L}_{3}N$ Coster-Kronig transition probability, ${L}_{2}\ensuremath{-}{L}_{3}M$ transitions being energetically impossible in this region. The following values are found: for Hg, ${f}_{{L}_{2}{L}_{3}}=0.08\ifmmode\pm\else\textpm\fi{}0.02$; for Ta, ${f}_{{L}_{2}{L}_{3}}=0.20\ifmmode\pm\else\textpm\fi{}0.04$. The x-ray coincidence experiments show that the average number of x-ray quanta emitted after creation of a primary vacancy in the ${L}_{2}$ subshell is ${\ensuremath{\nu}}_{{L}_{2}}=0.42\ifmmode\pm\else\textpm\fi{}0.02$ for Hg and ${\ensuremath{\nu}}_{{L}_{2}}=0.31\ifmmode\pm\else\textpm\fi{}0.01$ for Ta. Subshell fluorescence yields are found to be ${\ensuremath{\omega}}_{{L}_{2}}=0.39\ifmmode\pm\else\textpm\fi{}0.03$ and ${\ensuremath{\omega}}_{{L}_{3}}=0.40\ifmmode\pm\else\textpm\fi{}0.02$ for Hg; ${\ensuremath{\omega}}_{{L}_{2}}=0.25\ifmmode\pm\else\textpm\fi{}0.02$ and ${\ensuremath{\omega}}_{{L}_{3}}=0.27\ifmmode\pm\else\textpm\fi{}0.01$ for Ta.