Measurement ofL-shell photoelectric cross sections in highZ elements at 37 and 74 keV

L-shell photoelectric cross section measurements have been made at 36·818 and 74·409 keV for four elements in the range 81 ≤Z ≤ 92. The measurements at 74·409 keV are found to agree with theory, within experimental uncertainties, but the experimental values at 36·818 keV are found to be higher than the theoretical predictions. The possible reasons for the observed discrepancy are discussed.     

Total attenuation cross-sections of fluorescent X-rays of Zr,Sn, Ba,Au, Pb,Th and U in elements 6⩽Z⩽82

The total attenuation cross-sections in elements 6?Z?82 forK _α andK _β groups of lines of elements Zr, Sn and Ba andL _l ,L _α,L _β andL _γ groups of lines of the elements Au, Pb, Th and U have been measured. The experimentally measured attenuation cross-sections have been found in good agreement with the theoretical estimates.     

Measurement of angular distribution of M shell fluorescent X-rays excited by 5·95 keV photons in thorium

The differential cross-sections for the emission of M shell fluorescent X-rays from Th by 5·95 keV photons at eight angles ranging from 50° to 120° have been measured. The differential cross-section is found to decrease with increase in the emission angle showing anisotropic spatial distribution of M shell fluorescent X-rays. The present results contradict the predictions of the calculations of Cooper and Zare [1] that the atomic inner shell vacancy states produced in photoionization are not aligned but confirm those of Fluggeet al [2] and Scofield [3] that the vacancy states withJ > 1/2 are aligned. The integral M shell fluorescent emission cross sections have been determined from the measured angular distribution coefficients and compared with theoretical integral cross-sections calculated by using theoretical values of M subshell photoionization cross-sections, fluorescence yields and coster kronig transition probabilities available in literature. The experimental and theoretical values of integral crosssections show a reasonable agreement.     

Measurement of total M shell photoionization cross sections for Au,Pb, Th and U in the energy region 6–12 keV

The total M shell relative photoionization cross-sections for Au, Pb, Th and U have been measured in the energy region 6–12 keV. External conversion K X-rays of suitable elements has been employed as incident photons to photo ionize the total M shell of elements under investigation. The method provides relative cross-sections therefore does not make use of theoretically calculated average M shell fluorescence yields which involve uncertainties of the order of 20%. No evidence of deviation from calculated values of cross-sections have been observed within experimental errors for all incident photon energies.     

Determination ofL-shell X-ray production cross-sections in holmium by 10–40 keV photons

In an effort to resolve the existing discrepancy between experiment and theory, the cross-sections for the production ofL _l,L _α ,L _β andL _γ groups ofL-shell X-rays of Ho by photons of nine energies in the range 10–40 keV have been measured using an improved version of annular source double reflection geometrical set-up. Contrary to the earlier findings of Garget al that the measured values of the cross-sections are consistently higher than those calculated theoretically, the present results do not confirm this. The plausible deficiencies in the experiments of Garget al are pointed out and possible remedies to overcome them are suggested. It is concluded that the higher values obtained by Garget al are probably due to systematic errors in their method of measurement.     

Measurement ofL III subshell photoelectric cross-sections in highZ-elements

L _III subshell photoelectric cross-sections in lead, thorium and uranium at 13·596, 16·896 and 17·781 keV respectively have been determined. The results are found to agree well with theory.     

Measurement ofL-shell photoelectric cross sections in highZ elements at 60 keV

L-shell photoelectric cross sections have been measured at 60 keV for six elements in the range 74≤Z≤92. The measurements are found to agree with theoretical calculations.     

Measurement ofL-shell photoelectric cross-sections in lower intermediateZ elements at 6 keV

L-shell photoelectric cross-sections have been measured at 6 keV for eight elements in the range 40⩽Z⩽53. The measurements agree with theoretical calculations.     

Experimental investigation of angular dependence of photon induced L-shell X-ray emission intensity

The angular dependence of emission intensity of L shell X-rays induced by 59.57 keV photons in Pb and U is investigated by measuring the normalized intensities of the resolved L X-ray peaks at different angles varying from 40° to 120°. It is observed that while L _l and L_α X-ray peaks (originating fromJ = 3/2 state) show some anisotropic angular distribution, the emission of L_β and L_γ X-ray peaks is isotropic. The present results contradict the calculations of Co-oper and Zare (1969) that after photoionization of inner shell, the vacancy state has equal population of magnetic substates and the subsequent X-ray emission is isotropic but confirm the predictions of Fluggeet al (1972) that the atomic inner shell vacancies produced after photoionization are aligned and the x-ray emission from the filling of vacancies in state withJ ⩾ 3/2 is anisotropic.