Laser isotope fractionation

Fortier SM, Cole DR, Wesolowski DJ, Riciputi LR, Paterson BA, Valley JW, Horita J (1995) Determination of the magnetite-water equilibrium oxygen isotope fractionation factor at 350°C a comparison of ion microprobe and laser fluorination techniques. Geochim Cosmochim Acta 59 3871-3875 Friedman I, O Neil JR (1977) Compilation of Stable Isotope Fractionation Factors of Geochemical Interest. US Geol Surv Prof Paper 440-KK... 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

To test for the possibility of laser-induced fractionation, we compared NIST standards in the TOF with both laser and nebulizer aspirated solutions (Figure 1). Our results indicate that while a small amount of bias correction difference exists between laser and aspirated sample introduction at lower signal intensities, no significant difference in isotopic ratios between ablated and aspirated samples exists when signal intensities are maintained at 300,000 cps and higher. 

Laser ablation Universal ionization high spatial resolution Low precision, poor reproducibility, isotopic fractionation... 

The laser typically used for laser ablation is the frequency quadrupled Nd YAG (266 nm) with a pulse width of a few nanoseconds. With this laser, some fractionation will occur. Unless a good external standard is used, quantification of the elements in the sample is difficult if not impossible. This is not an impediment to use of laser ablation in the field of radiochemistry or radionuclides. One of the most important aspects of radionuclide analysis is determining isotope ratios of elements of interest. All isotopes of a particular element behave the same when removed from a solid sample by a laser pulse. Ionization of those isotopes can depend on the laser bandwidth and polarization so care must be used when using lasers for direct ionization of atomic species. 

Isotope Fractionation During Laser Ablation and Ionization... 

Investigation on elemental and isotopic fractionation during 196 nm femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry. Spectrochim. Acta B, 62, 410-422. 

The nature and sources of laser-induced isotopic fractionation in laser ablation... 

Jackson, S. E. and Gtlnther, D. (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J. Anal. At. Spectrom., 18, 205-12. 

Since these early studies, efforts have concentrated on expanding the number of isotope systems to which LA-MC-ICP-MS can be applied, and mechanisms to correct for inter-element interference, mass bias and laser-induced isotopic fractionation. Where possible, internal normalisation of data using fractionation factors determined from a pair of stable isotopes of the element under investigation is the preferred route of data correction. Where this is not possible, external normalisation using another element at similar mass is used but, especially at light masses, this approach may not readily correct for laser-induced preferential volatilisation of lighter isotopes which may vary on an element-by-element basis. ... 

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