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Isotope fractionation occurs during a phase transition, when the ratio of light to heavy isotopes in the involved molecules changes.When water vapor condenses (an equilibrium fractionation), the heavier water isotopes (18 O and 2 H) become enriched in the liquid phase while the lighter isotopes (16 O and 1 H) tend toward the vapor phase.
The difference is whether the relative abundance is with respect to all the nitrogen, i.e. 14 N plus 15 N, or just to 14 N. Since the atmosphere is 99.6337% 14 N and 0.3663% 15 N, a is 0.003663 in the former case and 0.003663/0.996337 = 0.003676 in the latter.
Equilibrium isotope fractionation is the partial separation of isotopes between two or more substances in chemical equilibrium. Equilibrium fractionation is strongest at low temperatures, and (along with kinetic isotope effects) forms the basis of the most widely used isotopic paleothermometers (or climate proxies): D/H and 18 O/ 16 O records from ice cores, and 18 O/ 16 O records from calcium ...
Nitrogen-15 (15 N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15 N.Despite the different weights, 15 N is involved in the same chemical reactions as the more abundant 14 N and is therefore used to trace and quantify conversions of one nitrogen compound to another.
Figure 2 Figure 3 - Isotopic Fractionation Sources. The atoms hydrogen, oxygen, and carbon co-exist naturally in specific proportions with their stable isotopes, 2H (or D), 18O and 13C respectively, in different proportions as shown in the figure 2 below. The amount and distribution of the different isotopes in a molecule is influenced by: [5]
Since its original descriptions, the Urey–Bigeleisen–Mayer equation has taken many forms. Given an isotopic exchange reaction + = +, such that designates a molecule containing an isotope of interest, the equation can be expressed by relating the equilibrium constant, , to the product of partition function ratios, namely the translational, rotational, vibrational, and sometimes electronic ...
Denitrification can lead to a condition called isotopic fractionation in the soil environment. The two stable isotopes of nitrogen, 14 N and 15 N are both found in the sediment profiles. The lighter isotope of nitrogen, 14 N, is preferred during denitrification, leaving the heavier nitrogen isotope, 15 N, in the residual matter.
Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of 143(36) yoctoseconds , though the half-life of nitrogen-9 has not been measured exactly.