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Half-Life Measurements of $^{110}$ Sn, $^{113}$ Sn, $^{117\mathrm{m}}$ Sn, and $^{123\mathrm{m}}$ Sn Produced via Photon Activation of Natural Tin

This study reports new independent half-life measurements for $^{110}$ Sn, $^{113}$ Sn, $^{117\mathrm{m}}$ Sn, and $^{123\mathrm{m}}$ Sn produced via photon activation, confirming most existing nuclear data but revealing a statistically significant discrepancy for the $^{117\mathrm{m}}$ Sn isomer that warrants further investigation.

Original authors: O Nusair, D Devries, M Toto-Gonzalez

Published 2026-06-26

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: O Nusair, D Devries, M Toto-Gonzalez

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you have a box of different types of sand. In the world of nuclear physics, this "sand" is natural tin, a metal found in many everyday objects. Scientists want to know exactly how long certain "grains" of this sand (specifically, radioactive versions called isotopes) last before they disappear. This duration is called a half-life.

Think of a half-life like a magical hourglass. If you start with 100 grains of radioactive sand, the half-life is the exact amount of time it takes for half of them (50 grains) to vanish. Knowing this time precisely is crucial because scientists use these "sand grains" as clocks for everything from calibrating medical scanners to understanding how stars are born.

The Experiment: A High-Speed Light Show

To study these tin grains, the researchers at NorthStar Medical Radioisotopes didn't just wait for them to decay naturally. They used a giant, high-powered machine called a Rhodotron accelerator.

Imagine this accelerator as a super-fast slingshot. It fires a beam of electrons (tiny, fast-moving particles) at a target made of natural tin. When these electrons hit a special metal plate (a converter), they create a burst of high-energy light (gamma rays). This light then hits the tin target, "waking up" the tin atoms and turning them into the specific radioactive versions the scientists wanted to study: 110Sn, 113Sn, 117mSn, and 123mSn.

It's like shining a bright flashlight on a dark room to make specific objects glow so you can see them clearly.

The Watch: Listening to the Glow

Once the tin was "woken up," the scientists placed it next to a very sensitive detector (a High-Purity Germanium detector). Think of this detector as a super-accurate microphone that listens for the specific "notes" (gamma rays) the radioactive tin emits as it decays.

They didn't just listen once; they listened for months. They took snapshots of the "noise" (spectra) at different times to see how the glow faded.

110Sn was a quick flash, fading in just a few hours.
113Sn was a slow-burning candle, lasting over a hundred days.
117mSn was a medium-duration glow, lasting about two weeks.
123mSn was a very brief spark, lasting less than an hour.

The Puzzle: Measuring the Time

The scientists had to be very careful. The "notes" the tin emitted sometimes overlapped with notes from other elements, or the signal was messy at the edges. To solve this, they used advanced math (like fitting a curve through scattered dots) to isolate the exact signal for each tin isotope.

They compared their new measurements against the "official rulebook" of nuclear data (called the Nuclear Data Sheets or NDS), which is the standard reference everyone uses.

The Results: Mostly Agrees, One Big Surprise

Here is what they found:

110Sn, 113Sn, and 123mSn: Their measurements were very close to the official rulebook. It's like checking your watch against the atomic clock and finding you are only a few seconds off. This confirms the rulebook is correct for these isotopes.
117mSn (The Surprise): This one was different. The official rulebook says this isotope lasts 13.76 days. The scientists measured it to last 13.95 days.
- While that sounds like a tiny difference (less than 2%), in the world of high-precision physics, this is a huge gap.
- The paper uses a statistical tool called a "z-score" to measure this. For the other isotopes, the score was low (meaning they agreed). For 117mSn, the score was very high (4.6), which is like rolling a die and getting a 6 every single time. It's statistically impossible to be just a random fluke.

Why Does This Matter?

The paper explains that this specific isotope, 117mSn, is used in nuclear medicine. Doctors use it to treat bone cancer and to create images of the body.

Because the half-life determines how long the medicine stays active in a patient, the "clock" must be perfect. If the rulebook says the clock runs at one speed, but the real clock runs slightly faster, doctors might calculate the wrong dose.

The Paper's Claim: The authors state that their new measurement suggests the official value might be slightly off. They say this discrepancy is "statistically significant" and warrants further investigation.
The Implication: If the half-life is indeed longer than the rulebook says, it could affect how doctors plan treatments and calculate the radiation dose a patient receives.

Summary

In short, the scientists used a high-energy light beam to create radioactive tin, listened to it fade away for months, and found that three of the four types matched the official records perfectly. However, one type (117mSn) seems to last slightly longer than everyone thought. This isn't just a small error; it's a signal that the "rulebook" might need a correction, which is important for anyone using this isotope for medical treatments or scientific calculations.

Technical Summary: Half-Life Measurements of 110Sn, 113Sn, 117mSn, and 123mSn Produced via Photon Activation of Natural Tin

Problem Statement
Precise radionuclide half-lives are fundamental to applied and basic nuclear science, underpinning applications ranging from astrophysical reaction rate modeling and detector efficiency calibration to nuclear medicine dosimetry. While evaluated databases such as the Nuclear Data Sheets (NDS) provide recommended values, independent determinations using distinct production and counting methodologies are necessary to cross-check these data, reduce systematic uncertainties, and validate rate predictions. This study addresses the need for independent verification of the half-lives for four specific tin nuclides: 110Sn (relevant to astrophysical p-process modeling), 113Sn (a standard for HPGe calibration), 117mSn (used in nuclear medicine dosimetry), and 123mSn (relevant to nuclear data evaluations).

Methodology
The authors employed photon activation of natural tin targets using a TT-300HE Rhodotron accelerator at NorthStar Medical Radioisotopes.

Irradiation: Two irradiation campaigns were conducted. The primary campaign used a 6 mm tantalum (Ta) bremsstrahlung converter with a 40 MeV electron beam (1 µA current) to produce 113Sn, 117mSn, and 123mSn. A secondary campaign utilized a 36 MeV electron beam and a 3 mm tungsten (W) converter to specifically optimize the production of 110Sn for precise half-life determination.
Detection: Activated samples were monitored over several months using a high-purity germanium (HPGe) detector. Spectra were acquired with varying live times (3 min to 60 min) to capture both short-lived and long-lived isotopes.
Spectral Analysis:
- Calibration: Energy, resolution (FWHM), and efficiency calibrations were performed using standard reference sources (e.g., 229Th).
- Peak Fitting: Isotope-specific peak models were applied to handle complex spectral regions:
  - 110Sn (280.49 keV): Modeled as a mixture of two Exponentially Modified Gaussians (EMGs) with a piecewise linear background to account for low-energy tailing.
  - 113Sn (391.697 keV): Fitted with a single Gaussian plus linear background.
  - 117mSn (158.56 keV) and 123mSn (160.34 keV): These adjacent peaks were deconvolved using a triple-Gaussian model with a piecewise linear background to separate the 117mSn transition, the 123mSn transition, and a minor 117mSn low-energy component.
Data Processing: An iterative decay correction procedure was used. Activities were calculated from fitted peak areas, correcting for dead-time and counting intervals. Half-lives were refined by fitting the activity versus time data to a single-exponential decay model until convergence was achieved (relative change < 1%).

Key Contributions and Results
The study provides independent half-life determinations for the four isotopes, comparing them against NDS recommended values:

110Sn: Measured $T_{1/2} = (4.165 \pm 0.025)$ h. This agrees with the NDS value of $(4.154 \pm 0.004)$ h within uncertainties ( $z$ -score = 0.435).
113Sn: Measured $T_{1/2} = (116.08 \pm 0.94)$ d. This shows a relative deviation of ~0.86% from the NDS value of $(115.09 \pm 0.03)$ d ( $z$ -score = 1.053), remaining within combined uncertainties.
117mSn: Measured $T_{1/2} = (13.95 \pm 0.01)$ d. This exhibits a statistically significant deviation from the NDS recommended value of $(13.76 \pm 0.04)$ d. The difference corresponds to a $z$ -score of 4.608, indicating the discrepancy is unlikely to be due to random statistical fluctuations.
123mSn: Measured $T_{1/2} = (39.95 \pm 0.12)$ min. This is consistent with the NDS value of $(40.06 \pm 0.02)$ min ( $z$ -score = -0.904).

Significance and Claims
The paper claims that these results offer a critical cross-check of evaluated nuclear data using a distinct production route (photon activation) and high-resolution gamma-ray spectrometry.

Systematic Verification: For 110Sn, 113Sn, and 123mSn, the results generally agree with NDS values, reinforcing the reliability of current data for applications in astrophysics and calibration.
Discrepancy in 117mSn: The primary finding is the statistically significant deviation observed for 117mSn. The authors state this suggests a systematic difference warranting further investigation. They highlight that even small deviations in this isotope's half-life can propagate into decay-correction protocols, patient dose planning, and quantitative imaging in nuclear medicine, directly affecting absorbed dose estimates and therapeutic efficacy.
Methodological Rigor: The study emphasizes the value of independent determinations using distinct production routes to identify potential systematic errors in established datasets. The authors note that their approach minimizes contamination from competing reaction channels and strictly controls systematic effects (e.g., dead-time, precursor feeding), allowing for high-precision determinations with relative uncertainties below 1%.

The paper concludes that while most results align with current evaluations, the significant deviation in 117mSn underscores the necessity for periodic reevaluation of decay data, particularly for isotopes with critical applications in dosimetry and medical therapy.