In most of the lines 5
d
9
6
p
–5
d
8
6
8
2
the components due to
200
Hg,
202
Hg and
204
Hg have been resolved and term isotope shifts have been assigned for these isotopes for nearly all the terms of each configuration. Some less accurate data for
198
Hg,
199
Hg and
201
Hg are obtained from measurements on incompletely resolved components. An approximate magnetic hfs analysis for all terms of 5
d
9
6
p
and 5
d
8
6
8
2
has been made for
199
Hg. This analysis was made on the assumption that components of even isotopes always preserve the same relative spacing. The assumption does not appear to be strictly valid in a few cases, the largest departure apparently occurring in lines measured by Mrozowski (1942) involving the 5
d
8
½ ½
6
8
2
|
0
term (and possibly in two other lines). The magnetic hfs is compared with that expected for
jj
-coupling, and it conforms moderately well, but there is evidence of intermediate coupling effects in both configurations, especially 5
d
9
6
p
, and in one term at least of this configuration there is also indication of a small perturbation from 5
d
8
6
8
6
p
. By deducing the nuclear magnetic moment of
199
Hg the results are shown to be tolerably consistent with previous investigations. The isotopic structures are very regular compared with those reported for the isoelectronic Pt I spectrum. Such small irregularities as have been found are discussed; those found in 5
d
8
6
8
2
do not seem to be due to the nuclear ‘volume’ effect.
Isotope shifts inNe20,22: Precision measurements and global analysis in the framework of intermediate coupling
