Theoretical and Experimental Understanding of the Anomalous Odd-to-Even Isotope Ratios of Tin in a 1 + 1 Single-Colour Resonance Ionization Mass Spectrometry: Revisited

Abstract

Differences in the odd to even response for tin isotopes has been observed earlier in resonance ionization experiments, resulting in anomalous odd to even isotope ratios. I have used a theoretical approach known as the spectral simulation approach to understand the cause for such anomaly and the anomaly has also been experimentally verified and found to be in good agreement. The effects of laser parameters such as intensity, accuracy of the excitation laser wavelength and bandwidth on the determination of the tin isotope ratio have been analyzed theoretically and experimentally. The source for such anomalies was found to be the inaccuracy in the excitation laser wavelength. For the 5p 2 ( 3 P 0 ) − 5p 6s ( 3 P 0 1 ) (286.3317 nm) transition, an inaccuracy of the order of γ L in the peak frequency of the excitation laser (γ L = 15 GHz) can cause anomalies as large as ∼31% (β = 0.31). Use of a very large bandwidth laser (∼60 GHz) reduces the anomaly to as small as −0.003. Alternatively by employing a relatively narrow band laser (∼1.2 GHz), it has been observed that inaccuracy of the order of 3-4 γ L in the laser peak frequency does not induce anomalies >0.05. The isotope ratio is sensitive to the inaccuracy in the excitation laser wavelength for an intermediate linewidth laser.

Broadband non‐selective excitation of plutonium isotopes for isotope ratio measurements in resonance ionization mass spectrometry: a theoretical study

“…In order to determine the isotope ratios by RIMS, this inherent selectivity of the photo‐excitation process should be eliminated by indiscriminate excitation of all the constituent isotopes. Thus, the corresponding isotopic ratio is determined without much bias . In the present case, approaching such an ideal condition is by no means a simple task considering the large isotope shifts of the plutonium isotopes.…”

“…Thus, the corresponding isotopic ratio is determined without much bias. [31][32][33][34] In the present case, approaching such an ideal condition is by no means a simple task considering the large isotope shifts of the plutonium isotopes. The obvious choice for isotope ratio measurements would be to use a very broadband laser, so that the entire spectral width of all the isotopes is overlapped and all the isotopes are excited.…”

Pb‐Pb Dating of Terrestrial and Extraterrestrial Samples Using Resonance Ionization Mass Spectrometry

“…We routinely observed fractionated 207 Pb/ 206 Pb ratios in standards, due to a well‐known odd‐even isotope effect in resonance ionization (e.g., Fairbank et al, 1989; Sankari, 2011). The odd‐even isotope effect is known to be very sensitive to laser wavelength.…”