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Nuclear Science Division

A New Way to Make Element 116 Opens the Door to Heavier Atoms

Researchers at the 88-Inch Cyclotron successfully made superheavy element 116 using a beam of titanium-50. That milestone sets the team up to attempt making the heaviest element yet: 120.

Today, an international team of researchers led by Berkeley Lab’s Heavy Element Group announced that they have made known superheavy element 116 using a titanium beam, a breakthrough that is a key stepping stone towards making element 120. The result was presented today at the Nuclear Structure 2024 conference; the science paper will be posted on the online repository arXiv and has been submitted to the journal Physical Review Letters.

Half-life of 71Ge and the Gallium Anomaly

Experiments detecting neutrinos via the (νe, e−) reaction on 71Ga systematically observe lower than expected interaction rates. This unexplained phenomenon, demonstrated most recently by the BEST experiment with a high statistical significance [1], is known as the “gallium anomaly.” The discrepancy is so far unexplained and could be an exciting potential indicator of new neutrino physics [2,3]. However, it has been pointed out that a larger value of the half-life of 71Ge (12.5 – 13.5 days vs. 11.43 days measured in 1985 [4,5]) used to compute the neutrino cross sections on 71Ga could reduce or eliminate the anomaly [6] and that new measurements were needed [7]. 

This question is thoroughly addressed in E.B. Norman et al.’s new paper, “Half-life of 71Ge and the gallium anomaly,” published on May 30th 2024 in Physical Review C [8] as an Editor’s Suggestion. The authors from UC Berkeley, LBNL, and LLNL carried out three separate high-precision spectral measurements with planar HPGe detectors at the LLNL Nuclear Counting Facility: the rate of electron capture decay of 71Ge to 71Ga was measured directly, as well as in relation to 57Co and 55Fe radioactive standards. In the latter technique, fitting the ratio of the 71Ge activity to that of the well-known standard provides a measure of the difference in their decay rates, while eliminating many systematic effects. Figs. 2 and 3 show the spectra and the decay rate fits, respectively. 

Both germanium oxide and crystalline High Purity germanium samples were utilized, with the latter prepared at LBNL’s Semiconductor Detector Laboratory (SDL) by NSD Research Scientist Alexey Drobizhev. The material was irradiated in the graphite reflector of the McClellan Nuclear Research Center (MNRC) TRIGA reactor at UC Davis to create the relatively short-lived 71Ge isotope. The samples were counted continuously for over two months at LLNL. NSD’s Yury Kolomensky contributed to the high quality statistical analysis featured in this paper. 

The final result gives a 71Ge half-life of 11.468 ± 0.008 days—fully consistent with prior measurements (Fig. 1), while significantly more precise. Importantly, it rules out the longer half-life values that would be needed to explain the neutrino event deficit seen by gallium experiments. Thus, the gallium anomaly remains a mystery with potential for more beyond-the-standard model physics in the neutrino sector. 

Figure 1: Results from all reported measurements of the 71Ge half- life since 1985 [8].
Figure 2: Relevant portions of measured spectra, after 24h of counting. Top: 71Ge; middle: 71Ge + 55Fe; bottom: 71Ge + 57Co [8].
Figure 3: Decay curves from three measurements of the 71Ge half-life. Top: Ga K-shell x-rays from the standalone 71Ge source; middle: the ratio of Ga to Mn K-shell x-rays from 71Ge + 55Fe; bottom: ratio of Ga K-shell x-rays to 14-keV γ-rays from 71Ge + 57Co. Left and right plots represent two different analyses [8].

References
[1] V. V. Barinov et al., Results from the Baksan experiment on sterile transitions (BEST), Phys. Rev. Lett. 128, 232501 (2022) DOI: https://doi.org/10.1103/PhysRevLett.128.232501
[2] J. N. Abdurashitov et al., Measurement of the response of a Ga solar neutrino experiment to neutrinos from a 37Ar source, Phys. Rev. C 73, 045805 (2006) DOI: https://doi.org/10.1103/PhysRevC.73.045805
[3] M. Laveder, Unbound neutrino roadmaps, Nucl. Phys. B 168, 344 (2007) DOI: https://doi.org/10.1016/j.nuclphysbps.2007.02.037
[4] B. Singh and J. Chen, Nuclear structure and decay data for A = 71 isobars, Nucl. Data Sheets 188, 1 (2023) DOI: https://doi.org/10.1016/j.nds.2023.02.001
[5] W. Hampel and L. P. Remsberg, Half-Life of 71Ge, Phys. Rev. C 31, 666 (1985) DOI: https://doi.org/10.1103/PhysRevC.31.666
[6] C. Giunti, Y. F. Li, C. A. Ternes, and Z. Xin, Inspection of the detection cross section dependence of the gallium anomaly, Phys. Lett. B 842, 137983 (2023) DOI: https://doi.org/10.1016/j.physletb.2023.137983
[7]  S. R. Elliott, V. Gavrin, and W. Haxton, The gallium anomaly, arXiv:2306.03299v1 DOI: https://doi.org/10.48550/arXiv.2306.03299
[8] E.B. Norman et al. “Half-life of  71Ge  and the gallium anomaly.” Phys. Rev. C 109, 055501 (2024) DOI: https://doi.org/10.1103/PhysRevC.109.055501

NSD’s Wick Haxton elected to the American Philosophical Society

The American Philosophical Society in May announced its Members elected to the Society in 2024. Election to the American Philosophical Society honors extraordinary accomplishments in all fields. The APS is unusual among learned societies because its Membership is composed of top scholars from a wide variety of academic disciplines. Wick Haxton was elected as part of the Mathematical and Physical Sciences class.

Wick C. Haxton
Distinguished Professor of Physics, University of California, Berkeley;
Senior Faculty Scientist, Lawrence Berkeley National Laboratory;
Professor Emeritus, University of Washington

Erich Leistenschneider named as award recipient for the 2024 Rare Isotope Beams (FRIB) Visiting Scholar Program

Erich Leistenschneider

Erich Leistenschneider, a Staff Scientist in the Accelerator-Based Low Energy Research Program has been selected as an award recipient for the 2024 Facility for Rare Isotope Beams (FRIB) Visiting Scholar Program for Experimental Science.  This award acknowledges Erich’s outstanding record and potential impact on the FRIB science program.  Further details can be found here.

Congratulations are also due to former NSD employee Yassid Ayyad, now with the University of Santiago de Compostela, who will also receive the award.

In Memoriam – Joe Cerny

Joseph Cerny, a distinguished member of the UC Berkeley Chemistry faculty and a Berkeley Lab senior staff member for more than five decades, died on April 17, 2024, after a long illness. Cerny’s distinguished scientific career included the first identification of two new modes of radioactive decay, for which he received the EO Lawrence Award in 1974 and the Nuclear Chemistry Prize of the American Chemical Society in 1977. As an administrator, Cerny held important positions on the UC Berkeley Campus and at the Berkeley Lab.  On campus, he chaired the Chemistry Department from 1975-80, and was Dean of the Graduate School from 1986-2000. Concurrently, he served first as Provost and then as Vice Chancellor for Research.  At Berkeley Lab, Cerny was Associate Director and head of the Nuclear Science Division from 1980-85.

Joseph (Joe) Cerny was born in Oxford, Mississippi, on April 24, 1936. He graduated with a BS degree in chemical engineering from the University of Mississippi in 1957 and then spent a year in the UK at the University of Manchester as a Fulbright Scholar before entering graduate school in the UC Berkeley Chemistry Department. His thesis research was conducted at the 60-Inch Cyclotron on the UC Berkeley Campus with Bernard Harvey as his advisor.

Upon completion of his PhD in 1961, Joe was appointed assistant professor, the start of a 52 year career as a faculty member in the Department of Chemistry at UC Berkeley. He also launched an independent research program at the Lawrence Radiation Laboratory (now the Lawrence Berkeley National Laboratory, or Berkeley Lab). During the Cuban Missile Crisis, Joe, who was a reserve Army Officer, spent one and a half years engaged in munitions research. Upon his return to Berkeley, he continued his research on exotic decays of proton-rich light nuclei using the newly-commissioned 88-Inch Cyclotron at Berkeley Lab. Joe also collaborated with Art Pozkanzer and Earl Hyde on studies of neutron-rich light nuclei using high energy proton beams at the Bevatron. In June 1978, Joe and Art reviewed the highlights of this field in an article on exotic light nuclei in Scientific American.

This phase of Joe’s career was recognized by the Ernest Orlando Lawrence Memorial Award of the Atomic Energy Commission (predecessor of the U.S. Department of Energy) in 1974, for his “discovery of proton emission as a mode of radioactive decay, for investigation of the limits of nuclear stability of a number of light elements, and for ingenious instruments that made these discoveries possible.” A few years later, in 1977, he was awarded the Nuclear Chemistry Prize of the American Chemical Society for this work and for the discovery of beta-delayed proton emission.  

Starting in 1974, Joe accepted a series of important leadership positions that would occupy a significant fraction of his energies for the next quarter century. On campus, he was appointed chair of the UC Berkeley Chemistry Department from 1974-1979. He was then appointed as associate director and division head of Berkeley Lab’s Nuclear Science Division from 1979 to 1985. Following a sabbatical leave at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, Joe returned to the UC Berkeley Campus as dean of the Graduate School and Provost in 1986. In 1994, the Provost’s responsibilities were broadened and he became Vice Chancellor for Research, continuing in this role until 2000.

Joe maintained his research group at the Lab, as well as his interest in ingenious instrumentation, throughout his years as a senior administrator on campus.  At his 60th Birthday Symposium in 1996, Joe proposed the construction of a beamline to bring unstable nuclei from a medical cyclotron at the laboratory down the hill to the 88-Inch Cyclotron, for reacceleration. This was successfully completed three years later, allowing some of the first experiments with accelerated beams of unstable isotopes. 

With his background in university teaching and research, it is no surprise that Joe was a strong advocate for educating the next generation of nuclear scientists, and he led an important study of this topic for the Department of Energy and the National Science Foundation in 2004.

Joe is survived by his sons, Keith and Mark, and four grandsons, from his marriage to Barbara Shirley. He is also survived by stepchildren and step-grandchildren from his marriage to Susan Dinkelspiel Cerny.

Friends and colleagues of Joe’s are invited to an informal Memorial Gathering at the UC Berkeley Faculty Club on Sunday, June 23rd.  Guests are invited from 2:00 p.m. onwards with a 2:30 p.m. start.  Light refreshments will be served.  Please RSVP to Joe’s daughter-in-law, Jennifer Cerny, at jennifermcerny@gmail.com for further details and parking instructions.