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Nuclear spin and progresses in study on separation and conversion
dynamics of nuclear spin isomers of ethylene
2017, 37 (6):
193-211.
PDF (1834KB)
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806
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The nucleus is composed of protons and neutrons. The total angular momentum of the protons
and neutrons in an atomic nucleus is usually referred to as nuclear spin. Nuclear spin isomers
and their stability are fundamental concepts in quantum mechanics, and all molecules possessing
identical nuclei with nonzero spin have two or more distinct nuclear spin isomers with different
arrangements of total nuclear spin quantum numbers. Thus, researchers have tried to separate the
nuclear spin isomers of gaseous polyatomic molecules and study the conversion mechanisms among
them for many years. However, the studies in this field did not make progress until the early 90s.
In 2005, we made a study on the separation and conversion of nuclear spin isomers of ethylene
for the first time, to which we gave a special introduction in this paper. Firstly, the scientific
history about the discovery of the protons and neutrons that form nucleus is briefly described
chronologically; the concept of nuclear spin isomers is presented, and the nuclear spin isomers
of hydrogen and ethylene molecules aref described in detail. Secondly, we give a full description
of the progresses made in the experimental study on the separating the nuclear spin isomers of
gaseous ethylene with light-induced drift technique, and make a quantitative explanation on the
interconversion dynamics among the nuclear spin isomers of ethylene based on parity conservation
and quantum relaxation theory. Finally, we briefly summarize the latest research finding. The
enrichment of the nuclear spin isomers of ethylene can be achieved through chemical synthesis
using the acetylene catalytically hydrogenated with para-hydrogen, which would sufficiently and
successfully enhance nuclear magnetic resonance signal.
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