New precise  K measurement as a test of internal conversion theory 166 keV transition in 139 La Christine Balonek Dr. John C. Hardy, Advisor Dr. Ninel Nica, Deputy Advisor August 3, 2006

Overview Internal Conversion 139 La Decay Scheme 139 Ba Source Data Collection Spectral Analysis Impurity Analysis K X-Ray Analysis  K Calculations Preliminary Results Summary Acknowledgements

Nuclear de-excitation energy transferred to an electron –Electron is emitted and followed by an x-ray –In competition with  -ray emission Internal Conversion Coefficient – Impact –Nuclear decay schemes Spin and parity assignments Transition rates Branching ratios –Detector calibration Internal Conversion x-ray e- ~ s e- ~ s  -ray L shell K shell Hole

139 La Decay Scheme Lanthanum K x-rays Energy (keV)Intensity 1 2 1 2 3

139 Ba Source Source design –Determine number of atoms (mass of sample) required to produce desired  -ray counts Preparation of sources –Obtain enriched barium –Dilute Ba(NO 3 ) 2 in water –Two sources, A and B Adhesive Mylar tape, 3.81  m Ba ++ (aq) + 2NO 3 - (aq) Insulin Mylar tape, 12.7  m Trim excess tape to minimize impurities Source ready to be irradiated 7.0 mm 0.5 in Layer Effects –Attenuation calculations –Back scattering

Data collection Neutron irradiation of source –Texas A&M Nuclear Science Center  and x-ray detection –Germanium detector, Cyclotron Institute, Texas A&M University Relative photopeak efficiencies calibrated to 0.15% –17 spectra recorded between ~1 and 24 hours after activation 151. mm  and x-rays

Spectral Analysis Source A, Sept irradiation, spectrum 1 –52.7 min elapsed time / 46.9 min live time (~0.6 half lives)

Impurity Analysis KK KK  -ray x-rays x-ray impurities keV to keV  -ray impurities keV to keV

K X-Ray Analysis Spectrum 1, 0.88 hr - largely 139 La x-rays Spectrum 9, hr - source impurity x-rays

K X-Ray Analysis spectrum 9, scaled spectrum 1 Lanthanum K x-ray region Impurities: 152 Eu m  152 Sm 152 Eu  152 Sm 152 Eu m  152 Eu 153 Sm  153 Eu

 K Calculation K-shell internal conversion coefficient,  K  K = K-shell fluorescence yield –0.905(4)* N K, N  = total number of K x or  -rays –Integration of spectra after removal of impurities  K,   = detector efficiency for K x or  -rays –Known detector efficiencies at energies of interest *E. Schönfeld, H. Ja  en, NIM A 369 (1996) 527.

Preliminary Results Source A, Sept IrradiationSource B, July 2006 Irradiation Theoretical Calculations

Summary Successfully prepared and irradiated two enriched 139 Ba sources Analyzed 17 spectra for impurities based on  -ray energies and parent nuclei properties Performed quantitative x-ray analysis to subtract impurities Calculated preliminary values for  K of 139 La More detailed analysis of x-rays needed –Analysis is ongoing Next: 196 Pt irradiation –  K measurement for 197 Au

Acknowledgements Dr. John C. Hardy, Advisor Dr. Ninel Nica, Deputy Advisor Hardy Research Group –Victor Golovko, John Goodwin, Victor Iacob, Hyo In Park Texas A&M Cyclotron Institute REU Program –Dr. Sherry Yennello –Mary Ann Batson