Editing Xenon (section)

=== Nuclear spin ===
Nuclei of two of the stable [[isotopes of xenon]], <sup>129</sup>Xe and <sup>131</sup>Xe (both stable isotopes with odd mass numbers), have non-zero intrinsic [[angular momentum|angular momenta]] ([[Spin (physics)|nuclear spins]], suitable for [[nuclear magnetic resonance]]). The nuclear spins can be aligned beyond ordinary polarization levels by means of circularly polarized light and [[rubidium]] vapor.<ref>{{cite journal
| last       = Otten
| first      = Ernst W.
| s2cid      = 51224754
| date       = 2004
| title      = Take a breath of polarized noble gas
| journal    = Europhysics News
| volume     = 35
| issue      = 1
| doi        = 10.1051/epn:2004109
| pages      = 16–20
| bibcode    = 2004ENews..35...16O
| doi-access = free
}}</ref> The resulting [[spin polarization]] of xenon [[atomic nucleus|nuclei]] can surpass 50% of its maximum possible value, greatly exceeding the thermal equilibrium value dictated by [[paramagnetic]] statistics (typically 0.001% of the maximum value at [[room temperature]], even in the strongest [[magnet]]s). Such non-equilibrium alignment of spins is a temporary condition, and is called ''[[hyperpolarization (physics)|hyperpolarization]]''. The process of hyperpolarizing the xenon is called ''optical pumping'' (although the process is different from [[optical pumping|pumping a laser]]).<ref>{{cite journal
| journal = Physical Review Letters
| volume  = 96
| issue   = 5
| page    = 053002
| year    = 2006
| title   = Optical Pumping System Design for Large Production of Hyperpolarized <sup>129</sup>Xe
| first   = I. C.
| last    = Ruset
| author2 = Ketel, S.
| author3 = Hersman, F. W.
| doi     = 10.1103/PhysRevLett.96.053002
| pmid    = 16486926
| bibcode = 2006PhRvL..96e3002R
}}</ref>

Because a <sup>129</sup>Xe nucleus has a [[Spin (physics)|spin]] of 1/2, and therefore a zero [[electric field|electric]] [[quadrupole moment]], the <sup>129</sup>Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and the hyperpolarization persists for long periods even after the engendering light and vapor have been removed. Spin polarization of <sup>129</sup>Xe can persist from several [[second]]s for xenon atoms dissolved in [[blood]]<ref>{{cite journal
| first      = J.
| last       = Wolber
| author2    = Cherubini, A.
| author3    = Leach, M. O.
| author4    = Bifone, A.
| title      = On the oxygenation-dependent <sup>129</sup>Xe t<sub>1</sub> in blood
| year       = 2000
| journal    = [[NMR in Biomedicine]]
| volume     = 13
| issue      = 4
| pages      = 234–7
| doi        = 10.1002/1099-1492(200006)13:4<234::AID-NBM632>3.0.CO;2-K
| pmid       = 10867702
| s2cid      = 94795359
| doi-access = free
}}</ref> to several hours in the [[gas phase]]<ref>{{cite journal
| first   = B.
| last    = Chann
| author2 = Nelson, I. A.
| author3 = Anderson, L. W.
| author4 = Driehuys, B.
| author5 = Walker, T. G.
| title   = <sup>129</sup>Xe-Xe molecular spin relaxation
| year    = 2002
| journal = Physical Review Letters
| volume  = 88
| issue   = 11
| pages   = 113–201
| doi     = 10.1103/PhysRevLett.88.113201
| pmid    = 11909399
| bibcode = 2002PhRvL..88k3201C
}}</ref> and several days in deeply frozen solid xenon.<ref>{{cite encyclopedia
| first     = Gustav Konrad
| last      = von Schulthess
| author2   = Smith, Hans-Jørgen
| author3   = Pettersson, Holger
| author4   = Allison, David John
| year      = 1998
| title     = The Encyclopaedia of Medical Imaging
| page      = 194
| publisher = Taylor & Francis
| isbn      = 1-901865-13-4
| url       = https://books.google.com/books?id=zvDY5unRC4oC&pg=PA194
}}</ref> In contrast, [[isotopes of xenon|<sup>131</sup>Xe]] has a nuclear spin value of {{frac|3|2}} and a nonzero [[quadrupole moment]], and has t<sub>1</sub> relaxation times in the [[millisecond]] and [[second]] ranges.<ref>{{cite journal
| first   = W. W.
| last    = Warren
| author2 = Norberg, R. E.
| title   = Nuclear Quadrupole Relaxation and Chemical Shift of Xe<sup>131</sup> in Liquid and Solid Xenon
| year    = 1966
| journal = Physical Review
| volume  = 148
| issue   = 1
| pages   = 402–412
| doi     = 10.1103/PhysRev.148.402
| bibcode = 1966PhRv..148..402W
}}</ref>