NMR properties:

Magnetogyric Ratio NMR frequency Natural abundance (NA) Nuclear spin (I) Quadrupole moment (Q) Reference sample
84 Kr
84 Kr
36

(Gr. kryptos, hidden) Discovered in 1898 by Ramsay and Travers in the residue left after liquid air had
nearly boiled away. In 1960 it was internationally agreed that the fundamental unit of length, the meter,
should be defined in terms of the orange-red spectral line of 86Kr. This replaced the standard meter of
Paris, which was defined in terms of a bar made of a platinum-iridium alloy. In October 1983 the meter,
which originally was defined as being one ten millionth of a quadrant of the earth's polar circumference,
was again redefined by the International Bureau of Weights and Measures as being the length of a path
traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
Sources
Krypton is present in the air to the extent of about 1 ppm. The atmosphere of Mars has been found to
contain 0.3 ppm of krypton. Solid krypton is a white crystalline substance with a face-centered cubic
structure which is common to all the "rare gases."
Properties
It is one of the "noble" gases. It is characterized by its brilliant green and orange spectral lines.
Isotopes
Naturally occurring krypton contains six stable isotopes. Seventeen other unstable isotopes are now
recognized. The spectral lines of krypton are easily produced and some are very sharp. While krypton is
generally thought of as a rare gas that normally does not combine with other elements to form
compounds, it now appears that the existence of some krypton compounds is established. Krypton
difluoride has been prepared in gram quantities and can be made by several methods. A higher fluoride
of krypton and a salt of an oxyacid of krypton also have been reported. Molecule-ions of ArKr+ and
KrH+ have been identified and investigated, and evidence is provided for the formation of KrXe or
KrXe+.