K.S. Kahlon

Experimental investigation of alignment of the L3 subshell vacancy state produced after photoionisation in lead by 59.57 keV photons

Experimental investigation of the alignment of the L3 subshell vacancy state produced after photoionisation in lead by 59.57 keV photons has been reported. The results confirm the prediction of the calculations of Flugge et al (1972) that the atomic inner-shell vacancies produced after photoionisation are aligned and the X-ray emission from the filling of vacancies in states with J>or=3/2 is anisotropic, but contradict the predictions of Cooper et al. (1969) that after photoionisation of the inner shell, the vacancy state has an equal population of magnetic substates and the subsequent X-ray emission is isotropic.

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 Ll and Lα X-ray peaks (originating fromJ = 3/2 state) show some anisotropic angular distribution, the emission of Lβ and Lγ 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.

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 ofLl,Lα,Lβ andLγ 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.

Alignment of M-subshell vacancy states after photoionization

Alignment of M-subshell vacancy states after photoionization in Pb by 5.959 keV photons has been reported. The present results contradict the predictions of Cooper and Zare (1969) that, after photoionization of inner shells, the vacancy state has equal population of magnetic substates and the subsequent X-ray emission is isotropic, but confirm the predictions of the calculations of Flugge et al. (1972) that the atomic inner-shell vacancies produced after photoionization are aligned and the X-ray emission from the filling of vacancies in states with J>1/2 is anisotropic.

Thick target bremsstrahlung spectra produced by 204Tl beta particles in the photon energy region of 10–30 keV

Total bremsstrahlung (BS) spectra in thick targets of Al, Ti, Sn and Pb targets produced by complete absorption of 204Tl beta particles are studied at photon energy from 10 keV to 30 keV. The experimental BS spectra measured with X-PIPS Si(Li) detector are compared with the theoretical BS spectra obtained from Elwert corrected (non-relativistic) Bethe–Heitler theory and modified Elwert factor (relativistic) Bethe–Heitler theories, with and without the contributions of polarization bremsstrahlung in a stripped atom approximation, described by Avdonina and Pratt (1999 J. Phys. B: At. Mol. Opt. Phys. 321 4261). It is observed that the experimental results show better agreement with the modified Elwert factor (relativistic) Bethe–Heitler theory having the contribution of polarization bremsstrahlung at photon energy from 10 keV to 30 keV. This indicates that the polarization bremsstrahlung must be taken into account while studying the spectral photon distributions produced by continuous beta particles in thick target materials.

Effect of external magnetic field on attenuation coefficient for magnetic substances

The measurement of attenuation coefficient of some magnetic substances, to include diamagnetic: Cu, Zn, Ag, Te, Au, Pb, and Perspex; paramagnetic: Al, Ti, Mo, Dy, Ho, and Pt and ferromagnetic substances: Fe, Co, Ni, Gd, FeO, NiO, FeS, and Fe2O3, both in the presence and absence of an external magnetic field has been carried out using narrow beam transmission geometry by using gamma ray photons of incident energy 59.54keV from 100mCi, 241Am point source. It was observed very keenly that the value of linear attenuation coefficient of various substances mentioned above decreased remarkably. It varied in the range of 1-2%, 2-6% and 6-9% for diamagnetic, paramagnetic and ferromagnetic substances respectively in the presence of an external magnetic field. Measured results elucidated it very clearly that linear attenuation coefficient at H=0T, 0.6T and 1.2T continued to decrease with a regular increase of magnetic field. It is also manifested that measurements of linear attenuation coefficient is not affected with the change in thickness of the given substance. Within error limits (1-3%) variations are observed with increases of thickness along with magnetic field. Further to it the obtained results of linear attenuation coefficient without magnetic field (H=0T) were compared with theoretical data tables of FFAST and WinXCOM. It was established that values obtained are well within the experimental errors. To the best of our knowledge no other study in relation to the effect of linear attenuation coefficient in the presence of magnetic field available as precedence.

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.

Effect of applied mechanical stress on absorption coefficient of compounds

The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al2O3, CaCO3, ZnO2, SmO2 and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.