M. Schmidt et al., Temperature dependence of the optical response of sodium cluster ions Na-n(+), with 4 <= n <= 16, PHYS REV B, 59(16), 1999, pp. 10970-10979
The temperature dependence of the optical response of small sodium cluster
ions, Na-n(+) (n = 4,..,,16), was measured. At low temperature (35 to 100 K
) individual lines are seen, whose peak positions agree with ab initio calc
ulations if the geometric positions of the atoms in the cluster are taken i
nto account. The peaks broaden slowly with increasing temperature and coale
sce, until at high temperature only one, two, or three broad peaks remain,
whose positions are for n greater than or equal to 7 in good agreement with
the nearly free-electron model. Although the detailed shape of the optical
spectra changes strongly with temperature, its moments are nearly temperat
ure independent. No pronounced effect due to the solid to liquid phase tran
sition has been observed for these small cluster sizes. [S0163-1829(99)1371
5-9].