INVESTIGATIONS OF SPECTRAL DISTRIBUTION OF

COMPTON SCATTERED GAMMA RAYS FROM K-SHELL

ELECTRONS OF TIN USING 662 keV PHOTONS

JAGJIT KAUR, R. DEWAN, BHAJAN SINGH, B. S. SANDHU andB. S. GHUMMAN

Physics Department, Punjabi University, Patiala-147002, India

For bound electrons, Compton scattering deviatessigni®cantly from Klein-Nishina values. Many in-vestigators (Kane, 1992) work with di�erent tech-

niques involving various approaches to understandthis deviation. The common conclusion of these stu-dies is that K-shell Compton scattering cross-sec-

tions are signi®cantly smaller than Klein-Nishinavalues at small scattering angles and the K-shellCompton peak is broadened. Some authors haveshown the presence of infra red divergence and an

high energy tail. But the results regarding the shiftof the K-shell Compton peak from the free electronpeak are not conclusive. Some authors predict posi-

tive defect while others show no defect or negativedefect. To investigate the shift of Compton peaksfrom free electron peaks we have measured the

spectral distribution of Compton scattered gammarays from K-shell electrons of tin at 662 keV atscattering angles of 20, 25, 30, 50 and 110 degrees.

The experimental arrangement used in the presentmeasurement has been discussed earlier(Kaur et al.,1996). An 8 curie Cs±137 radioactive source prop-

erly shielded with lead is used to obtained 662 keVgamma rays. A thin uniform tin foil having thick-ness of 30 mg cm-2 and diameter 40 mm was used

as scatterer. Two NaI(Tl) spectrometers working incoincidence were used to record events. Theobserved spectra show a broadening of the peak

but this broadening is quite small as predicted byvarious theories. The results obtained are shown inTable 1. Peaks at all angles are shifted to the highenergy side and the presence of infra red divergence

and high energy tails have not been observed.

REFERENCES

Kane, P. P. (1992) Inelastic scattering of X-Rays andGamma rays by Inner shell electrons. Physics Reports218, 67.

Kaur, J., Singh, B., Sandhu, B. S. and Ghumman, B. S.(1996) Measurement of K-shell Compton scatteringfrom tin at 662 KeV gamma rays using ¯uorescencegamma coincidence technique. J. Instrument Soc, India26(3), 52.

Radiat. Phys. Chem. Vol. 51, No. 4±6, p. 377, 1998# 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain0969-806X/98 $19.00+0.00PII: S0969-806X(97)00145-X

Table 1. Peak position, FWHM and defect in Compton shift in experimental spectra at various angular positions

y in degrees Free electron Compton peak K-shell electron Compton peak

Theory (keV) Expt. (keV) FWHM (keV) Expt keV FWHM(keV) Defect (keV)

20 613.7 612 104 628 130 +1625 590.1 590 100 612 128 +2230 563.8 564 94 588 122 +2450 452.4 452 82 478 116 +26110 241.7 240 60 262 102 +22

377