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 5p2(3P0) 5p 6s () (286.3317 nm) transition, an inaccuracy of the order of in the peak frequency of the excitation laser ( GHz) can cause anomalies as large as 31% (). Use of a very large bandwidth laser (60 GHz) reduces the anomaly to as small as . Alternatively by employing a relatively narrow band laser (1.2 GHz), it has been observed that inaccuracy of the order of 3-4 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.
Highlights
Resonance ionization mass spectrometry (RIMS) has emerged as a powerful analytical technique for applications where isotopic selectivity is of prime concern [1, 2]
Near-resonance ionization Mass Spectrometry (NRIMS) is based on the principle that, if ionization occurs on a time scale shorter than the hyperfine precession period, the measured response will not be altered by the hyperfine coupling, and the isotope ratios measured using such a method should in principle represent the true abundances in the sample
The response of 115Sn >117Sn >119Sn was observed by Fairbank et al [3] in sputter-initiated resonance ionization of tin isotopes which was inferred by them as not real and presumed to be an artifact due to insufficient correction for the count rate
Summary
Resonance ionization mass spectrometry (RIMS) has emerged as a powerful analytical technique for applications where isotopic selectivity is of prime concern [1, 2]. RIMS has the ability to eliminate isobaric interferences and promises to be an ideal technique for isotope ratio measurements Such isotope ratio measurements are feasible only if the laser can indiscriminately ionize all the isotopes with equal efficiency. Fairbank et al [3] have observed an anomaly of about ∼31% in the odd-to-even response for tin and ∼15% for molybdenum when broadband lasers are used [4, 5] Such anomaly is not expected since the linewidth of the excitation laser is twice the frequency spread of the transition. An alternative approach for understanding the anomaly in the odd to even isotope ratios of tin isotopes for relatively broadband lasers has been discussed Using such an approach, it is ascertained that the inaccuracy in the peak frequency of the excitation laser to be the source for such anomalies in the odd to even isotope response of tin isotopes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
