Laser Isotope Separation and Spectroscopy Techniques

Laser isotope separation exploits the slight differences in atomic energy levels between isotopes to achieve selective excitation and ionisation. By tuning narrowband or broadband lasers to transitions unique to a target isotope, atoms can be driven through stepwise excitation into autoionising or continuum states, yielding ion beams of high isotopic purity. Complementary spectroscopy techniques, notably resonance ionisation spectroscopy and high-resolution laser spectroscopy of hyperfine structures and isotope shifts, provide critical information on level energies, lifetimes and nuclear properties. Together, these methods underpin applications ranging from the production of medical and industrial isotopes to fundamental studies in nuclear and atomic physics, with continuous advances in laser technology, theoretical modelling and experimental schemes enhancing selectivity, throughput and efficiency.

Research from Nature Portfolio

Recent studies have refined three-step photoionisation schemes to separate heavy and rare isotopes with unprecedented purity and production rates. A theoretical investigation into radium isotopes demonstrated that optimised laser bandwidths, power densities and timing can yield 223Ra with 98.5 % radio-isotopic purity at 0.74 μg h^–1, sufficient for large-scale medical applications. Parallel work on neodymium has modelled a resonant three-step scheme for the enrichment of 150Nd, showing that 50 kg of material at 66 % enrichment could be produced in five months of continuous operation, thereby supporting next-generation double-beta decay experiments. Foundational efforts in lutetium separation have also shown that combining continuous-wave excitation with pulsed ionisation using off-the-shelf lasers can achieve near-100 % enrichment of 176Lu at production rates up to 5 mg h^–1, streamlining the supply chain for medical isotopes.

Research from all publishers

A growing body of work in laser spectroscopy has expanded the toolkit for both separation and fundamental studies. High-resolution resonance ionisation spectroscopy of lutetium has mapped forty-seven odd-parity autoionisation levels, measured state lifetimes and extracted Fano line-shape parameters to guide efficient multi-step ionisation schemes. Complementary experiments using multi-mode lasers and time-of-flight mass spectrometry have resolved hyperfine A and B constants, as well as isotope shifts, in the 609 nm transition of natural and medical isotopes of lutetium, informing both atomic structure models and separation pathways. In-source laser spectroscopy of dysprosium at a radioactive-beam facility has provided precise isotope shifts and extracted changes in mean-squared charge radii, illustrating the versatility of laser methods for on-line isotope identification and separation in facility environments.

Laser Isotope Separation and Spectroscopy Techniques publication trend

The graph below shows the total number of articles in laser isotope separation and spectroscopy techniques across all publications each year (not limited to Nature Index journals).

Technical terms

Photoionization: A multi-step laser excitation process in which an atom absorbs photons to reach an autoionising or continuum state, resulting in ion formation.

Autoionizing state: A quasi-bound atomic or ionic state above the ionisation threshold that decays spontaneously by ejecting an electron.

Rydberg state: A highly excited atomic state with principal quantum number n≫1, often used as an intermediate for selective ionisation.

Isotope shift: The change in atomic transition frequency between isotopes, arising from mass and volume (field) effects on the nucleus.

Hyperfine structure: The small energy splittings of atomic levels due to interactions between nuclear moments (magnetic dipole or electric quadrupole) and the electronic environment.

Resonance ionisation spectroscopy: A sensitive spectroscopic technique that employs resonant laser excitation combined with ion detection to study atomic and nuclear properties with high selectivity.

References

1. Laser isotope separation of 223Ra. Scientific Reports (2023).
2. Enrichment of 150Nd for neutrinoless double-beta decay detection. Scientific Reports (2022).
3. Laser isotope separation of 176Lu through off-the-shelf lasers. Scientific Reports (2021).
4. Resonance ionization spectrum of autoionization states of lutetium atom. Acta Physica Sinica (2023).
5. Hyperfine structure of the 609 nm transition of Lu I by RIMS with multi-mode lasers. Optics Continuum (2024).
6. In-source laser spectroscopy of dysprosium isotopes at the ISOLDE-RILIS. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms (2020).