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What Is Internal Conversion? Our Measurement Impurity Corrections

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What Is Internal Conversion? Our Measurement Impurity Corrections Precise Measurement of !T for the 39.76-keV E3 Transition in 103Rh A Further Test of Internal Conversion Theory Vivian Sabla1,2, N. Nica2, and J.C. Hardy2 1 Middlebury College, Middlebury, VT 05753 2 Cyclotron Institute, Texas A&M University, College Station, TX 77840 Theory - What is Internal Conversion? Our Measurement Impurity Corrections Internal Conversion is a process that occurs when an • 103 excited atom decays. When the atom decays, either a "-ray is We activated a source of Pd through thermal neutron • We fit the peaks of the "-rays, x-rays and impurities using the emitted or the energy from the nucleus is transferred to an inner- activation in the TRIGA reactor at Texas A&M University gf3 program in the Radware package. orbital electron, knocking the electron from the atom. Internal • 103Pd decays through electronic capture to 103Rh with a half-life • 111Ag impurity contributed to our x-ray package. We were able conversion is this process of transferring energy to an electron. of 16.991 days. to correct for the x-ray impurity using: When the inner-orbital electron is bumped out of the atom, a • Source “cooled down” for three weeks before we began our higher energy electron jumps down to fill its place, emitting a A(342γ) gamma spectroscopy allowing for short-lived radioactive A(Cd Kx)= ✏ph(23.6keV ) I(23.6keV ) characteristic x-ray in the process. impurities to decay away ✏ph(342γ) I(342γ) ⇥ ⇥ The ratio of the probability of internal conversion to the ⇥ probability of "-emission is called the Internal Conversion • Decay spectra were taken using our precisely efficiency • Our 40-keV gamma peak was confirmed to be the product of calibrated HPGe Detector. Coefficient, !T. random coincidence summing of K!-K! x-rays resulting from Our experimental method equates the probabilities to • Three series of spectra were recorded for a total of 24 days of the counting rate of the HPGe detector. intensities letting us measure the x-ray and "-peaks to determine spectra taken over a total of 81 days after activation. • Using the ratio between K! and K# x-rays, we found the K!- !T. K! peak area through the K!-K# peak at 42-keV. Impurity Analysis • The 42-keV peak was first corrected to account for an x-ray 182 "-ray P I impurity of Ta ↵ = e = e Pγ Iγ • Insight into what impurity isotopes might affect our x-ray and 1 1 gamma peaks of interest Preliminary Results P = P I = I e x e x 1 Nx ✏γ 1 !K =0.809(4) ! ! ! • Impurities found: ↵T =( ↵K ) 1 ! N ✏ − P − ✏γ =1.0103 1 N ✏ 1 K γ x EC,K x γ • 111Ag, 110mAg, 182Ta, 192Ir, 198Au, random coincidence ✏ =0.9042 ↵T =( ↵K ) 1 N = 86444813(9574) K !K Nγ ✏x − PEC,K − 103 x internal conversion summing of Pd x-rays ↵K = 131.3(39) "-ray emission N = 87397(2203) process γ PEC,K =0.8589 Theory (with hole)1 Theory (no hole)1 Our Result Motivation Ag 342.13 keV 111 Impurities 1404 1389 1437(44) Ta 67.75 keV Ir 316.52 keV 182 Au 411.80 keV 192 198 Ag 657.76 keV • ICC’s can be theoretically calculated using two methods, 110m yielding different results: Our result is consistent with our previous calculations which demonstrated that the atomic vacancy must be considered in ICC • Considering the atomic vacancy calculations. • Assuming atomic vacancy is filled too rapidly to effect the Further work on this project aims to decrease the uncertainty ICC value on our value caused by the trouble with the random coincidence summing of x-rays. • There are no other experiments that measure Internal Conversion Coefficients to less than 1% precision Acknowledgements/References • Our previous measurements demonstrate that the atomic vacancy must be considered in theoretical calculations • I would like to sincerely thank Dr. Ninel Nica and Dr. John Hardy for their support throughout this project. • Our aim with this work is to extend the applicability of that statement to Z=45, the lowest atomic number we have yet to • This work was made possible by the National Science measure. Foundation Grant No. PHY-1263281 and the Department of Energy Grant No. DE-FG03-93ER40773. • This experiment is a continuation of our series of high- precision ! measurements. x-ray package fit 342-keV " fit 1 T. Kibédi, et al., Nucl. Instr. and Meth. A 589 (2008) 202-229.
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