The Pb-207 isotope has an atomic weight of 207. It has 82 protons and 125 neutrons. Because it is stable, it is useful in estimating the relative isotope fractions of lead in earth’s atmosphere. This nuclide is also an indicator of radiogenic lead.
Radiogenic lead occurs as a result of decay from uranium and thorium. It is commonly referred to as “lead-lead dating.” In this technique, a fixed ratio of lead-204 to the primordial lead isotopes is used as a baseline to estimate radiogenic lead in rocks.
Several different uranium and thorium dating schemes can be used to determine the age of rock formations. In addition, the 207Pb/206Pb isochron method can be used to determine the age of meteorites. However, it is important to note that the 206Pb/204Pb isochron is only a crude method of determining the age of a meteorite. Using the newly-developed 235U and 238U decay constants, the Angra dos Reis meteorite is about 27 x 106 years old.
The 207Pb signal exhibits a positive slope of 0.70 +- 0.02 ppm K-1. This chemical shift is a response to subtle changes in the chemical environment. The chemical shift increases with increasing temperature. Higher spinning speeds of the 207Pb nucleus cause a split in the chemical shift.
As a result, the Pb-207 signal has a chemical shift range of 750 to 1260 ppm downfield of aqueous Pb(NO3)2. These signals are highly sensitive to temperature variations. Consequently, this sample could be used as a calibrating solid-state NMR probe.