Nuclear States Research Articles

High voltage determination and stabilization for collinear laser spectroscopy applications.

Fast beam collinear laser spectroscopy is the established method to investigate nuclear ground state properties such as the spin, the electromagnetic moments, and the charge radius of exotic nuclei. These are extracted with high precision from atomic observables, i.e., the hyperfine splitting and the isotope shift, which become possible due to a large reduction of the Doppler broadening by compressing the velocity width of the ion beam through electrostatic acceleration. With the advancement of experimental methods and applied devices, e.g., to measure and stabilize the laser frequency, the acceleration potential became the dominant systematic uncertainty contribution. To overcome this, we present a custom-built high-voltage divider, which was developed and tested at the German metrology institute, and a feedback loop that enabled collinear laser spectroscopy to be performed at a 100-kHz level. Furthermore, we describe the impact of field penetration into the laser-ion interaction region. This affects the determined isotope shifts and hyperfine splittings if Doppler tuning is applied, i.e., the ion beam energy is altered instead of scanning the laser frequency. Using different laser frequencies that were referenced to a frequency comb, the field penetration was extracted laser spectroscopically. This allowed us to define an effective scanning potential to still apply the faster and easier Doppler tuning without introducing systematic deviations.

Controlling 229Th isomeric state population in a VUV transparent crystal

The radioisotope thorium-229 (229Th) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and 229Th has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the 229Th isomer are imperative. Here we report the population of the 229Th isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent 229Th-doped CaF2 crystal. The decay half-life is measured to 447(25) s, with a transition wavelength of 148.18(42) nm and a radiative decay fraction consistent with unity. Furthermore, we report a new “X-ray quenching” effect which allows to de-populate the isomer on demand and effectively reduce the half-life. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes.

BIKINI ATOLL, NEVADA, MOSCOW. WASHINGTON’S LONG ROAD TO THE PARTIAL TEST BAN TREATY (1958–1963)

The conclusion of the 1963 Moscow Treaty banning nuclear weapon tests in the atmosphere, in outer space and under water is an important milestone in the history of the Cold War. It was preceded by long and complex negotiations between the USSR and the US. Measures to impose a moratorium on tests (August 1958 — August 1961) did not yield signifi cant results either in reducing harmful environmental consequences or in reducing the risk of nuclear conflict. In addition, the issue of at least partial test ban was closely linked to the political contradictions between the superpowers, in particular, regarding the status of Berlin. On 9 September 1961, the negotiations were stopped. In the fall, the USSR conducted a large series of explosions, and advances in weapons development required new tests. Moscow’s decision to withdraw from the moratorium was dictated by the desire to demonstrate to its opponents the readiness for any emergency. In 1962, the events around Cuba led not only to intensified testing by both powers, but also to the acute Cuban Missile Crisis in October, when the danger of using nuclear weapons became quite real. The August 1963 treaty was one of the immediate outcomes of the Cuban Missile Crisis. However, it is also important that the superpowers came to the signing of the Moscow Treaty only after their scientific and technological achievements (including, above all, the results of nuclear tests) had been able to ensure a confident strategic deterrence of each other. The tests of nuclear devices conducted by both powers in 1961 and 1962 allowed them to equip all types of carriers with warheads as part of their planned programs to renew strategic nuclear arsenals. At the same time, the Moscow Treaty created a basis for harmonizing the positions of the US and the USSR with regard to nuclear nonproliferation for many years to come.

Overhauser enhanced liquid state nuclear magnetic resonance spectroscopy in one and two dimensions

Nuclear magnetic resonance (NMR) is fundamental in the natural sciences, from chemical analysis and structural biology, to medicine and physics. Despite its enormous achievements, one of its most severe limitations is the low sensitivity, which arises from the small population difference of nuclear spin states. Methods such as dissolution dynamic nuclear polarization and parahydrogen induced hyperpolarization can enhance the NMR signal by several orders of magnitude, however, their intrinsic limitations render multidimensional hyperpolarized liquid-state NMR a challenge. Here, we report an instrumental design for 9.4 Tesla liquid-state dynamic nuclear polarization that enabled enhanced high-resolution NMR spectra in one and two-dimensions for small molecules, including drugs and metabolites. Achieved enhancements of up to two orders of magnitude translate to signal acquisition gains up to a factor of 10,000. We show that hyperpolarization can be transferred between nuclei, allowing DNP-enhanced two-dimensional 13C–13C correlation experiments at 13C natural abundance. The enhanced sensitivity opens up perspectives for structural determination of natural products or characterization of drugs, available in small quantities. The results provide a starting point for a broader implementation of DNP in liquid-state NMR.

Impact of Zeeman and hyperfine interactions on the magnetic properties of paramagnetic metal ions: II. Super-hyperfine interactions with surrounding nuclei

The anisotropic Zeeman and strong hyperfine interactions of a Kramers ion can significantly affect its magnetic properties as well as the interactions with the nearby nuclei. The interactions with the local environment are described in the preceding article. In the current work, the change of the spin states of distant nuclei is studied. Analytical expressions describing the depth of the electron spin echo envelope modulation (ESEEM) are obtained for the ions with anisotropic Zeeman and strong hyperfine interactions. Due to the g-tensor anisotropy, the electron Zeeman interaction axis is tilted in respect to the direction of the external magnetic field which makes non-collinear with the Zeeman interaction axes of the ion and the nearby nuclei and significantly modifies the nuclear spin states. Thus, the isotropic hyperfine interaction, and particularly the Fermi contact interaction can directly contribute to the ESEEM. An additional factor, that can significantly modify the ESEEM signal is the mixing of the multiple oscillations arising when several nuclei occur in optimal conditions for the generation of the nuclear coherence. This situation arises when several EPR transitions of the ion covering a wide range of magnetic fields are examined.

Shell-model representations of the microscopic version of the Bohr–Mottelson collective model

The structure of the irreducible collective spaces of the group Sp(12, R), which many-particle nuclear states are classified according to the chain Sp(12, R) ⊃ U(6) ⊃ SO(6) ⊃ SU pn (3) ⨂ SO(2) ⊃ SO(3) of the proton–neutron symplectic model (PNSM), is considered in detail. This chain of the PNSM was recently shown to correspond to a microscopic shell-model version of the Bohr–Mottelson collective model. The construction of the relevant shell-model representations of the Sp(12, R) group along this chain is considered for three nuclei with varying collective properties and from different mass regions. It is shown that the SU pn (3) basis states of the Sp(12, R) representations belonging to the SO(6) irreps with seniority υ ≥ υ 0, with υ 0 denoting the maximal seniority SO(6) irrep contained in the Sp(12, R) bandhead, are always Pauli allowed, but organized in a different way into different SO(6) shells. This is in contrast to the case of filling the levels of the standard three-dimensional harmonic oscillator and using the plethysm operation. Although the SU pn (3) multiplets within υ < υ 0 are not all Pauli forbidden, it is safe to discard them. The results obtained in the present work are important for the practical application of the microscopic version of the Bohr–Mottelson collective model.

How many nuclear weapons does Russia have? The size and characteristics of the Russian nuclear stockpile

Putin’s war of aggression against Ukraine, backed by frequent nuclear threats, has focused attention on the scope of Russia’s nuclear capabilities. The short assessments the United States Government provides are inadequate. Because of the very limited U.S. government information on the scope of Russia’s nuclear capabilities, the Federation of American Scientists (FAS) estimates are cited globally as if authoritative and definitive; they clearly are not. The numerous FAS numbers are largely undocumented and little documentation apparently exists to support their data. It is possible that the Russian nuclear force may be in the size range that the FAS estimates but it is also possible that it is twice as large or even larger. The Russian nuclear advantage may already be several to one and it is growing. The Russian advantage is particularly notable in non-strategic nuclear weapons. An accurate understanding of Russia’s nuclear capability is a critical element in shaping America’s nuclear deterrence requirements.

North Korean nuclear weapons, 2024

ABSTRACT North Korea continues to modernize and grow its nuclear weapons arsenal. In this Nuclear Notebook, the authors cautiously estimate that North Korea may have produced enough fissile material to hypothetically build up to 90 nuclear warheads, but has likely assembled fewer than that—potentially around 50. To deliver the warheads, North Korea is enhancing and diversifying its missile force, most recently with new solid-fuel long-range strategic missiles, short-range tactical missiles, and sea-based missiles. The Nuclear Notebook is researched and written by the staff of the Federation of American Scientists’ Nuclear Information Project: director Hans M. Kristensen, associate director Matt Korda, research associate Eliana Johns, and program associate Mackenzie Knight. To see all previous Nuclear Notebook columns in the Bulletin of the Atomic Scientists dating back to 1987, go to https://thebulletin.org/nuclear-notebook/.

Laser Excitation of the ^{229}Th Nuclear Isomeric Transition in a Solid-State Host.

LiSrAlF_{6} crystals doped with ^{229}Th are used in a laser-based search for the nuclear isomeric transition. Two spectroscopic features near the nuclear transition energy are observed. The first is a broad excitation feature that produces redshifted fluorescence that decays with a timescale of a few seconds. The second is a narrow, laser-linewidth-limited spectral feature at 148.382 19(4)_{stat}(20)_{sys} nm [2020 407.3(5)_{stat}(30)_{sys} GHz] that decays with a lifetime of 568(13)_{stat}(20)_{sys} s. This feature is assigned to the excitation of the ^{229}Th nuclear isomeric state, whose energy is found to be 8.355 733(2)_{stat}(10)_{sys} eV in ^{229}Th:LiSrAlF_{6}.

Cross-correlated relaxation in the NMR of near-equivalent spin pairs: Longitudinal relaxation and long-lived singlet order.

The evolution of nuclear spin state populations is investigated for the case of a 13C2-labeled triyne in solution, for which the near-equivalent coupled pairs of 13C nuclei experience cross-correlated relaxation mechanisms. Inversion-recovery experiments reveal different recovery curves for the main peak amplitudes, especially when the conversion of population imbalances to observable coherences is induced by a radio frequency pulse with a small flip angle. Measurements are performed over a range of magnetic fields by using a sample shuttle apparatus. In some cases, the time constant TS for decay of nuclear singlet order is more than 100 times larger than the time constant T1 for the equilibration of longitudinal magnetization. The results are interpreted by a theoretical model incorporating cross-correlated relaxation mechanisms, anisotropic rotational diffusion, and an external random magnetic field. A Lindbladian formalism is used to describe the dissipative dynamics of the spin system in an environment of finite temperature. Good agreement is achieved between theory and experiment.

The impact of the Ukraine war on Russian military capabilities in the Arctic

ABSTRACT This study examines the impact of the two-year occupation of Ukraine on Russia’s military capabilities in the Arctic and analyzes the strengths and weaknesses of Russia’s military capacity in this region. Using a methodology based on document analysis and SWOT analysis, the study aims to unravel the intricate interplay between the Ukraine conflict and Russia’s military aspirations in the Arctic and thereby improve our understanding of the military implications of these developments. The results of the study highlight a remarkable imbalance in Russia’s military capabilities in the vast Arctic region, which stretches across the western, central, and eastern sectors. The ongoing conflict in Ukraine is acting as a catalyst, forcing Russia to strengthen its conventional forces and improve its military readiness in the immediate future. As a result, there is a discernible inclination to prioritize nuclear capabilities as part of Russia’s strategic calculus in the Arctic region.

High-resolution laser spectroscopy on the hyperfine structure and isotope shift of 237,239\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{237,239}$$\\end{document}Np

Nuclear ground state properties of 237,239\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{237,239}$$\\end{document}Np were investigated by high-resolution laser spectroscopy at the RISIKO mass separator off-line radioactive beam facility of the University of Mainz. The isotope shifts and the hyperfine parameters were determined in two different atomic ground-state transitions at 398.80 nm and 395.61 nm. The data allowed for calculation of the so far unknown nuclear moments of the short-lived isotope 239\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{239}$$\\end{document}Np, i.e. the nuclear magnetic dipole moment of μI\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _I$$\\end{document} = +3.18(2) μN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _N$$\\end{document} and the electric quadrupole moment of QS\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q_S$$\\end{document} = +4.05(8) eb, using the known nuclear moments of 237\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{237}$$\\end{document}Np as a reference, which were determined by electron paramagnetic resonance and investigations of muonic X-ray hyperfine structures, respectively.

New methods to strengthen NMR signals

Stronger alignment of atomic nuclei in Nuclear Magnetic Resonance (NMR) would enable significantly more detailed MRI scans. We spoke to Professor Malcolm Levitt, Bonifac Legrady and Mohamed Sabba about how they generated hyperpolarised nuclear states which provide a very strong NMR signal, how they plan to maintain the hyperpolarised states for a long time under ambient conditions, and the wider implications of their research.

Reconsidering the Overlooked Threat of North Korea's Outer Space Activities: Focusing on the Menace of Militarization and Weaponization of Outer Space

What security implications do North Korea's purported peaceful space activities have? North Korea's recent launch of a reconnaissance satellite not only raises concerns about its nuclear weapons program but also has broader implications for international security. The nuclear threat posed by North Korea is certainly growing. However, there seems to be an overlooked security threat in North Korea's space initiative: the threat of militarization and weaponization of outer space. Therefore, the security policy toward North Korea must be changed comprehensively to address the militarization and weaponization of space, as North Korea's threats can be transformed by the use of space. North Korea's destructive weapons and strategies, such as EMP attacks and space hybrid operations, are not prohibited, even when they appear to be aligned with the outer space legal regime. Hence, rather than concentrating only on nuclear weapons, this study proposes that a fundamental shift in policy is required.

North Korea's Evolving Perception of China: From Kim Jong Il to Kim Jong Un and the Evolution of Pyongyang's Nuclear Strategy

North Korea has shown more aggressive nuclear behavior during the Kim Jong Un era as has been evident in the rapid acceleration of its nuclear weapons development and its delivery system diversification, especially in 2016. This study seeks to determine why was there such an urgency in progressing its nuclear capability in the first few years following Kim Jong Un's ascent to power after the death of his father in 2011. It confines its research scope to Pyongyang's external motivations - its political and economic relations with the biggest regime backer, China - to conduct an academic investigation on whether Kim Jong Un's North Korea could still perceive China as a reliable patron. It concludes that the bilateral political and economic relations took a notable and simultaneous downturn, prompting it to focus on internal balancing, exemplifying the core principles of the IR theory of defensive realism.

“Making Democracy Safe for the World”: Kenneth Waltz on Realism, Democracy, and War

Abstract This paper reevaluates the history of how some anti-war realists have assessed the relationship between democracy and armed conflict. To do so, I turn to a central realist figure: Kenneth Waltz. Drawing on newly available archival sources and his published work, I explore Waltz’s shifting relationship with American democracy, foreign policymaking, and war. I focus on his career-long anti-war commitments, tracing his foreign policy engagements over the half century of his academic career. Early on, Waltz argued in favor of American democracy as a source of adaptive, effective foreign policy. Gradually, however, his views shifted. After the Cold War and especially after 9/11, his anti-war beliefs and belief in democratic foreign policymaking came increasingly into tension. He moved from defending American democratic foreign policymaking to calling for structural constraints from without. We see this in Waltz’s late-life endorsement of the Iranian nuclear program, which was motivated not just by his well-known optimism about proliferation, but also by the hope that an Iranian nuclear arsenal would deter American intervention in the Middle East. Waltz’s experience has implications both for how we read his body of work and for how we understand realist attempts to shape foreign policy.

Spin-flip-induced quadrupole resonance in odd- A exotic atoms

We examine the possible existence of quadrupole resonances in exotic atoms containing odd-A nuclei. We find that the spin flip of the deexciting exotic particle can induce a resonance, altering the orbital angular momentum of the nucleus by one quantum. This process results in an excited nucleus with a suppression in x-ray photon emissions during the exotic atom cascade. We provide specific cases of antiprotonic atoms of stable elements where this resonance effect is expected to occur. The study of this phenomena may provide insight into the strong interaction of deeply bound antiprotonic states in the proximity of the unpaired nucleon, and serve as a tool for probing short-lived excited nuclear states. Published by the American Physical Society 2024

Direct WIMP detection rates for transitions in isomeric nuclei

The direct detection of dark matter constituents, in particular the weakly interacting massive particles (WIMPs), is central to particle physics and cosmology. In this paper we study WIMP induced transitions from isomeric nuclear states for two possible isomeric candidates: Ta180 and Ho166. The experimental setup, which can measure the possible decay of Ta180 induced by WIMPs, was proposed. The corresponding estimates of the half-life of Ta180 are given in the sense that the WIMP-nucleon interaction can be interpreted as ordinary radioactive decay.

Germany as a Nuclear Power?: How Nuclear Taboo Shaped the Discourse on West German Nuclearization

A disinformation campaign by the Adenauer administration in the 1950s has led the public to believe that West Germany has never had any intentions on gaining nuclear capabilities. This interpretation is not accurate, as modern research shows and opens a new area of research to be explored. Modern literature on the topic however has mostly been dealing with the problem of German nuclearization from an historical background. While there has been some research on the topic from an international relations perspective, such research has been conducted mostly from a realist perspective. Although the realist perspective has some merits, it is lacking in explanatory power when it comes to the words and behavior of German policy makers and politicians. Constructivist theory of the ‘nuclear taboo’ offers a good supplementary explanation for inner political dynamics during the 1950s and early 1960s. This research examines debates in the Bundestag related to the nuclearization of West Germany during those periods and takes a closer look at what and how congresspeople discussed West Germany going nuclear. It proves that nuclear taboo embraced by the congresspeople discouraged West Germany’s nuclearization.

Feasibility and Safeguards Policy for Nuclear Power Plants: A Case Study in Indonesia within the NPT Framework, Emphasizing Global Security Analysis

This study examines the feasibility of a United Nations (UN) peacekeeping force with nuclear capabilities to improve global security. It starts with a historical overview of nuclear weapons and international agreements. The research then addresses challenges such as proliferation, cyber threats, and nuclear energy expansion. This paper analyses Indonesia's stance on the Iranian nuclear issue and the challenges of balancing international relations with domestic pressures, with a focus on its role in the UN Security Council. Using a descriptive qualitative approach, the research assesses global security, technical challenges, political considerations, moral implications, cost allocation, roles of non-nuclear states, regional impacts, transparency, nuclear disarmament, public perception, and alternative security approaches. The study highlights the importance of a comprehensive evaluation that takes into account technical, political, ethical, economic, and regional dimensions. The text emphasizes the importance of transparency, accountability, and international consensus in achieving effective global security. While acknowledging both the potential benefits and risks, the research recommends careful consideration and multilateral diplomatic efforts to promote global stability.