Nuclear isomers—metastable states of atomic nuclei that conserve high excitation energy for unexpectedly prolonged periods—are essential to deepening our grasp of complex nuclear architectures and astrophysical nucleosynthesis processes. Over the course of many years of experimental investigation, the GSI/FAIR consortium has detected a cumulative total of 192 nuclear isomers, a feat unmatched by any other research facility worldwide. Propelled by an innovative integration of particle acceleration and advanced detection instrumentation, these findings testify not only to methodological ingenuity but also to the relentless curiosity driving experimental nuclear science.

Central to the success at GSI is the extraordinary contribution of Dr. Ivan Kojouharov, whose career dedicated to nuclear spectroscopy catalyzed the co-discovery of 143 individual nuclear isomers—more than any other researcher globally. His expertise in developing high-performance germanium detector arrays proved vital in numerous experiments, enabling exquisite resolution when measuring gamma radiation emitted by isomeric transitions. Dr. Kojouharov’s extensive publication record underscores his pivotal role in expanding the nuclear landscape through meticulous data acquisition and nuanced analysis techniques.

The sophisticated accelerator complex at GSI is a cornerstone of this achievement, comprising an elaborate chain of devices starting with the Universal Linear Accelerator (UNILAC), proceeding through the heavy-ion synchrotron SIS18, and culminating in the Experimental Storage Ring (ESR). This multi-tiered infrastructure uniquely facilitates experimental access to virtually all elements present in the periodic table, allowing researchers to induce nuclear reactions and isolate exotic isotopes under controlled conditions. Crucially, the Fragment Separator (FRS) functions as an ingenious “sorting machine,” spatially segregating newly formed nuclear fragments post-collision and enabling targeted scrutiny for isomeric states.

Nuclear isomers themselves exhibit a striking deviation from typical nuclear behavior. While most nuclei shed excess energy instantaneously upon excitation, isomers are hindered from rapid decay by internal quantum mechanical selection rules and nuclear structural idiosyncrasies. This results in metastable configurations capable of holding onto energy for durations ranging from microseconds to years before gamma emission restores the nucleus to its ground state. Studying these isomers unravels intricate nuclear potential landscapes and contributes vital insights into stellar processes such as rapid neutron capture (r-process) nucleosynthesis, which governs the cosmic production of heavy elements.

Beyond fundamental inquiry, nuclear isomers hold promise for innovative technological applications, including usage in medical diagnostic imaging techniques through their unique decay signatures. Moreover, some isomers have sparked interest as candidates for ultra-precise nuclear clocks, which could surpass the accuracy of contemporary atomic clocks by exploiting nuclear transition frequencies less susceptible to environmental perturbations. These applied research directions are intertwined with ongoing efforts to decipher the fine structure of nuclear energy levels and decay pathways.

Prof. Michael Thoennessen’s meticulous compilation consolidates all verified scientific publications on nuclear isomers with half-lives exceeding 100 nanoseconds, standardizing knowledge across a broad temporal scale. This database update complements his longstanding stewardship of isotope discovery statistics—another domain where GSI maintains a premier global standing. Notably, the late Professor Hans Geissel held the record for the discovery of 279 isotopes, a testament to the continuous lineage of excellence fostered at the center.

The international scientific collaboration NUSTAR, hosted for the first major meeting since the February fire at GSI, exemplifies the vibrant research community engaged with the FAIR (Facility for Antiproton and Ion Research) project. NUSTAR scientists delve deeply into nuclear reactions mimicking astrophysical environments, striving to elucidate element formation mechanisms active within stars and explosive cosmic events. The communal synergy at FAIR offers fertile ground for breakthroughs in both experimental nuclear physics and astrophysics.

Looking ahead, the construction of the FAIR international accelerator center presages even more profound discoveries. As one of the world’s largest and most ambitious research infrastructures, FAIR integrates next-generation superconducting fragment separators (Super-FRS) poised to enhance isotope separation capabilities beyond those of the conventional FRS. This technological leap is expected to accelerate the discovery rate of isotopes and nuclear isomers, extending the experimental reach into previously inaccessible regions of the nuclear chart.

Professor Thomas Nilsson, Scientific Managing Director of both GSI and FAIR, articulates the institution’s vision succinctly: to replicate cosmic phenomena within a state-of-the-art laboratory environment and secure a commanding position atop the leaderboards of nuclear discoveries. The convergence of scientific ambition, technical innovation, and interdisciplinary collaboration embodied in FAIR and GSI illuminates promising avenues for unraveling universal mysteries encoded in nuclear matter.

In summation, the record-setting discovery of nuclear isomers at GSI/FAIR underscores a significant chapter in the annals of nuclear physics research. It exemplifies how precision instrumentation, comprehensive accelerator suites, and dedicated scholarship synergistically advance our understanding of atomic nuclei and their astrophysical significance. As FAIR progresses, the anticipation of uncovering new exotic states fuels excitement within the scientific community, reaffirming GSI’s stature as a crucible for nuclear innovation and cosmic exploration.

Subject of Research: Discovery and characterization of nuclear isomers

Article Title: Discovery of nuclear isomers

Web References: DOI: 10.1016/j.adt.2025.101767

Image Credits: © L. Weitz, GSI/FAIR

Keywords

Physics, Nuclear physics, Nuclear reactions

At the heart of this study lies the challenge of precisely controlling the polarization state of mid-infrared laser pulses with relativistic intensities—a regime where the electric field of the laser approaches or exceeds the atomic fields inside matter, pushing electrons to speeds near that of light. Polarization control in such extreme conditions is notoriously difficult yet essential for applications ranging from high-harmonic generation to particle acceleration and advanced spectroscopic techniques.

Traditional methods of polarization rotation rely mostly on static materials and magnetic fields, which become ineffective or impractical under the intense electromagnetic stresses borne by relativistic pulses. To circumvent these limitations, the research team designed a plasma-based rotator, exploiting the unique properties of magnetized plasma to induce a variable Faraday rotation effect that depends on the frequency of the incident light pulse.

Faraday rotation is a well-known magneto-optical phenomenon where the polarization plane of light rotates when it traverses a material subjected to a magnetic field parallel to the light’s propagation direction. The novelty introduced in this work is the dynamic modulation of this rotation as a function of frequency within a magnetized plasma environment, where electron dynamics and collective oscillations can be engineered to produce tunable polarization changes.

The experimental setup involves generating a magnetized plasma column, embedded with a carefully controlled external magnetic field, through which the mid-infrared laser pulses propagate. By tuning parameters such as plasma density, magnetic field strength, and pulse frequency, the researchers achieved a variable Faraday rotation effect with unprecedented control over relativistic light-matter interaction.

This magnetized plasma rotator offers a frequency-sensitive polarization rotation that can be dynamically adjusted, providing a versatile tool to manipulate the polarization state of relativistic pulses in the mid-infrared spectrum. This spectral range is particularly crucial given its applications in molecular fingerprinting, medical diagnostics, and emerging quantum technologies.

Under relativistic conditions, the interaction of light with plasma involves complex nonlinear effects, including self-phase modulation, relativistic self-focusing, and plasma wave excitation. The introduction of magnetization further enriches this interplay, enabling the fine-tuning of polarization states through frequency-dependent electron gyration dynamics—an effect that traditional optical materials cannot replicate under similar conditions.

Importantly, the research emphasizes the dual role of plasma as both a nonlinear medium capable of withstanding intense fields and a dynamic environment responsive to external magnetic tuning. This duality underpins the unique ability to realize a frequency-variable Faraday rotation in a regime previously inaccessible to conventional rotators.

Computational simulations combined with experimental validations confirmed the theoretical predictions of variable polarization rotation, showing that even subtle adjustments in plasma and magnetic parameters induce measurable changes in the output pulse polarization. These findings underscore the feasibility of practical device implementation for applications requiring ultrafast polarization control.

Moreover, the rotator design inherently supports high damage thresholds, overcoming the limitations imposed by solid-state materials susceptible to optical destruction under high intensities. The plasma medium self-regulates through its collective behavior, ensuring stability and longevity in handling relativistic pulses.

This research opens promising avenues for future photonics platforms where control over light properties at relativistic intensities is essential. Potential applications extend to ultrafast optical switching, polarization-sensitive diagnostics in plasma physics, and even the generation of circularly polarized high-harmonic emissions for probing chiral molecules and femtochemistry.

By demonstrating the tunable Faraday rotation effect in magnetized plasma, the study pioneers a novel class of optical components that operate effectively under extreme light-matter interaction regimes, suggesting a profound shift in how photonic devices can be engineered to manage ultrafast, high-power laser pulses.

These insights are not only fundamental to advancing our understanding of plasma optics but also critical for the development of next-generation laser systems used in high-energy physics experiments, advanced microscopy, and quantum information science, where precise polarization control is paramount.

The work also highlights the importance of interdisciplinary approaches that combine plasma physics, nonlinear optics, and materials science to overcome challenges inherent in manipulating relativistic laser pulses, setting a paradigm for future innovation at the intersection of these fields.

In essence, the magnetized plasma rotator represents a significant technological leap, pushing the boundaries of what is possible in ultrafast laser control and heralding new capabilities in mid-infrared photonics with broad implications across scientific research and applied technologies.

Subject of Research: Magnetized plasma-based polarization control of relativistic mid-infrared laser pulses through frequency-variable Faraday rotation.

Article Title: Magnetized plasma rotator for relativistic mid-infrared pulses via frequency-variable Faraday rotation.

Article References:
Li, DA., Zhang, GB., Pegoraro, F. et al. Magnetized plasma rotator for relativistic mid-infrared pulses via frequency-variable Faraday rotation. Light Sci Appl 15, 25 (2026). https://doi.org/10.1038/s41377-025-02047-x

Image Credits: AI Generated

DOI: 02 January 2026