Edwards, R. R.

Fink, R. W.

Miccoli, B. R.

Robinson, B. L.

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 8 Article 13 1955 Possibility of Weak Alpha Branching in Radium D B. R. Miccoli University of Arkansas, Fayetteville R. R. Edwards University of Arkansas, Fayetteville B. L. Robinson University of Arkansas, Fayetteville R. W. Fink University of Arkansas, Fayetteville Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Organic Chemistry Commons Recommended Citation Miccoli, B. R.; Edwards, R. R.; Robinson, B. L.; and Fink, R. W. (1955) "Possibility of Weak Alpha Branching in Radium D," Journal of the Arkansas Academy of Science: Vol. 8 , Article 13. Available at: https://scholarworks.uark.edu/jaas/vol8/iss1/13 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. 163THE POSSIBILITY OF WEAK ALPHA BRANCHING IN RADIUM DB. R. MICCIOLI, R. R. EDWARDS, B. L. ROBINSONand R. W. FINKUniversity of ArkansasUp to now, naturally occurring radium D has not been known to emit alpha-articles. However, work in the chemistry department at the University of Arkan-as has indicated that such a weak alpha branch may exist in the decay of radiumn .- in fact, preliminary study supports such a hypothesis. Nuclear shell theoryalso supports an argument for the enhanced stability of the alpha-decay daughter,jl206 ( leading to a measurable lifetime. The general decay scheme may be rep-resented as follows:!Pb210 (RaD) ! 22 years < Bi210(RaE) 5 days Po210 (RaF)|Hg206. 1 mj Pt202 T „/8-?--— -J-*_Pb206 ( stable) !T1206?yS"(?)ia?Hg202(stable) \AU2O2B-_ _P jThe enclosed portion represents lEe region under stuBy, and" tlTe question marksindicate unknown entities.The solution to this problem lies in the preparation of sufficient amountsof Hg . The present method is to isolate mercury from the radium D present inaged radon needles. The activity husbanded in this way is quite small, and whileitissufficient for some experiments, it is too small for others. Larger amountsof Hg might be produced by second-order neutron capture in highly enrichedHg2 , using the highest neutron flux facility available, such as the MTR reactorat Oak Ridge or at Arco, Idaho. Ifwe should fail to detect this reaction, weshould be able to set an upper limit for the product °>> where CT 2 is tnecross section for reaction Hg™5 (n, y )Hg2", and L is the decay constant ofHg206.One approach to the investigation of Hg2""will be to examine its possiblebeta-decay daughter, 4.3-minute Tl2"":Gross decay of a mercury fraction whichwas chemically separated from radium D by a sul fide separation, which does notprovide an adequate decontamination factor from polonium or bismuth, exhibiteda curve whose period of maximum growth occurred at 250 hours. This would ruleout the possibility that Hg20°decays to 4.3-minute Tl2^, but leaves the pos-sibility that it may decay to some unknown isomeric level in Tl , or that itmay decay by alpha emission. The neutron absorption cross- section of Tl hasbeen reported* as 0.77 barns by the pile-oscillator technique while the activa-tion cross section of 4.3-minute Tl°has been reported as only 0.10 barn. Thedifference is attributed to the existence of one or more long-lived isomericlevels in Tl , which is activated simultaneously. Shell structure predicts theexistence of many low-lying high-spin states in odd-odd Tl , which has 81 pro-tons and 125 neutrons, just one proton and one neutron short of a closed shell.The unknown isomeric level cannot be shortlived, for it either would feed the4.3-minute state and contribute to its activation cross section, or it would in-dependently beta-decay. The latter would hardly have escaped notice in the past.Moreover, it is doubtful that an ordinary lifetime (hours, days, or months)would have gone undetected. Thus, we predict that the isomeric level has a half-life either very long or similar to that of Tl2 (about 3 years).Another possibility is that Hg may be beta-stable, and decays by alphaemission. In early studies a 70-hour daughter of Hg has shown up. Furtherwork is planned to establish the identity of the 70-hour activity, which mightbe due to unknown Pt 2"2 decaying to a possible short-lived Au 2 daughter.That Tl might undergo orbital electron capture to Hg is also withinthe realm of speculation. We plan to test this idea by studying the ratio of X-ray-decay/beta-decay of aged (2 to 5 years) and young samples of long-irradiated"Neutron Cross- Sections,"U.S. Atomic Energy Commission Report AECU-2040.163Journal of the Arkansas Academy of Science, Vol. 8 [1955], Art. 13Published by Arkansas Academy of Science, 1955164 ARKANSAS ACADEMY OF SCIENCEelemental thallium. Should this ratio prove to be different between the youneand the old samples, it would indicate that the beta-decay and orbital electron-capture arise from states of different lifetime, and perhaps from differentnuclides. The next step would be to irradiate isotopically enriched thallium inan attempt to identify these states.We have established a reliable procedure for chemically isolating and decon-taminating the radium-D decay products involved to study their radiation charac-teristics. Our new technique, which supplants the unsatisfactory sulfide methodmentioned earlier, is based on the following principles: (1) that PbtNO*)* isinsoluble in fuming nitric acid; (2) that bismuth and polonium do not extractinto isoamyl acetate from a dilute nitric acid aqueous phase; and (3) that mer-cury can be stripped from the isoamyl acetate layer by 1M ammonium chlorideaqueous solution. Thus, a carrier- free techrique, easily adaptable for the iso-lation of any of these elements, is at hand for the separation, carrier- free, orradium-D, -E, and -F. The radiations emitted by Hg^ will first be investigated,using the following counting techniques; (1) gross alpha and beta decay in awindowless flow counter; (2) hard beta-decay through absorbers; and (3) gammadecay and energy by scintillation spectrometry.164Journal of the Arkansas Academy of Science, Vol. 8 [1955], Art. 13https://scholarworks.uark.edu/jaas/vol8/iss1/13

English

Possibility of Weak Alpha Branching in Radium D

ScholarWorks@UARK

Journal of the Arkansas Academy of ScienceVolume 8 Article 131955Possibility of Weak Alpha Branching in Radium DB. R. MiccoliUniversity of Arkansas, FayettevilleR. R. EdwardsUniversity of Arkansas, FayettevilleB. L. RobinsonUniversity of Arkansas, FayettevilleR. W. FinkUniversity of Arkansas, FayettevilleFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Organic Chemistry CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu.Recommended CitationMiccoli, B. R.; Edwards, R. R.; Robinson, B. L.; and Fink, R. W. (1955) "Possibility of Weak Alpha Branching in Radium D," Journal ofthe Arkansas Academy of Science: Vol. 8 , Article 13.Available at: http://scholarworks.uark.edu/jaas/vol8/iss1/13163THE POSSIBILITY OF WEAK ALPHA BRANCHING IN RADIUM DB. R. MICCIOLI, R. R. EDWARDS, B. L. ROBINSONand R. W. FINKUniversity of ArkansasUp to now, naturally occurring radium D has not been known to emit alpha-articles. However, work in the chemistry department at the University of Arkan-as has indicated that such a weak alpha branch may exist in the decay of radiumn .- in fact, preliminary study supports such a hypothesis. Nuclear shell theoryalso supports an argument for the enhanced stability of the alpha-decay daughter,jl206 ( leading to a measurable lifetime. The general decay scheme may be rep-resented as follows:!Pb210 (RaD) ! 22 years < Bi210(RaE) 5 days Po210 (RaF)|Hg206. 1 mj Pt202 T „/8-?--—-J-*_Pb206 ( stable) !T1206?yS"(?)ia? Hg202(stable) \AU2O2B-__P jThe enclosed portion represents lEe region under stuBy, and" tlTe question marksindicate unknown entities.The solution to this problem lies in the preparation of sufficient amountsof Hg . The present method is to isolate mercury from the radium D present inaged radon needles. The activity husbanded in this way is quite small, and whileitissufficient for some experiments, it is too small for others. Larger amountsof Hg might be produced by second-order neutron capture in highly enrichedHg2 , using the highest neutron flux facility available, such as the MTR reactorat Oak Ridge or at Arco, Idaho. Ifwe should fail to detect this reaction, weshould be able to set an upper limit for the product °>> where CT 2 is tnecross section for reaction Hg™5 (n, y )Hg2", and L is the decay constant ofHg206.One approach to the investigation of Hg2""will be to examine its possiblebeta-decay daughter, 4.3-minute Tl2"":Gross decay of a mercury fraction whichwas chemically separated from radium D by a sul fide separation, which does notprovide an adequate decontamination factor from polonium or bismuth, exhibiteda curve whose period of maximum growth occurred at 250 hours. This would ruleout the possibility that Hg20° decays to 4.3-minute Tl2^, but leaves the pos-sibility that it may decay to some unknown isomeric level in Tl , or that itmay decay by alpha emission. The neutron absorption cross- section of Tl hasbeen reported* as 0.77 barns by the pile-oscillator technique while the activa-tion cross section of 4.3-minute Tl ° has been reported as only 0.10 barn. Thedifference is attributed to the existence of one or more long-lived isomericlevels in Tl , which is activated simultaneously. Shell structure predicts theexistence of many low-lying high-spin states in odd-odd Tl , which has 81 pro-tons and 125 neutrons, just one proton and one neutron short of a closed shell.The unknown isomeric level cannot be shortlived, for it either would feed the4.3-minute state and contribute to its activation cross section, or it would in-dependently beta-decay. The latter would hardly have escaped notice in the past.Moreover, it is doubtful that an ordinary lifetime (hours, days, or months)would have gone undetected. Thus, we predict that the isomeric level has a half-life either very long or similar to that of Tl2 (about 3 years).Another possibility is that Hg may be beta-stable, and decays by alphaemission. In early studies a 70-hour daughter of Hg has shown up. Furtherwork is planned to establish the identity of the 70-hour activity, which mightbe due to unknown Pt 2"2 decaying to a possible short-lived Au 2 daughter.That Tl might undergo orbital electron capture to Hg is also withinthe realm of speculation. We plan to test this idea by studying the ratio of X-ray-decay/beta-decay of aged (2 to 5 years) and young samples of long-irradiated"Neutron Cross- Sections, "U.S. Atomic Energy Commission Report AECU-2040.163Journal of the Arkansas Academy of Science, Vol. 8 [1955], Art. 13Published by Arkansas Academy of Science, 1955164 ARKANSAS ACADEMY OF SCIENCEelemental thallium. Should this ratio prove to be different between the youneand the old samples, it would indicate that the beta-decay and orbital electron-capture arise from states of different lifetime, and perhaps from differentnuclides. The next step would be to irradiate isotopically enriched thallium inan attempt to identify these states.We have established a reliable procedure for chemically isolating and decon-taminating the radium-D decay products involved to study their radiation charac-teristics. Our new technique, which supplants the unsatisfactory sulfide methodmentioned earlier, is based on the following principles: (1) that PbtNO*)* isinsoluble in fuming nitric acid; (2) that bismuth and polonium do not extractinto isoamyl acetate from a dilute nitric acid aqueous phase; and (3) that mer-cury can be stripped from the isoamyl acetate layer by 1M ammonium chlorideaqueous solution. Thus, a carrier- free techrique, easily adaptable for the iso-lation of any of these elements, is at hand for the separation, carrier- free, orradium-D, -E, and -F. The radiations emitted by Hg^ will first be investigated,using the following counting techniques; (1) gross alpha and beta decay in awindowless flow counter; (2) hard beta-decay through absorbers; and (3) gammadecay and energy by scintillation spectrometry.164Journal of the Arkansas Academy of Science, Vol. 8 [1955], Art. 13http://scholarworks.uark.edu/jaas/vol8/iss1/13

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Possibility of Weak Alpha Branching in Radium D

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