  We studied monoatomic linear carbon chains stabilised by gold nanoparticles
attached to their ends and deposited on a solid substrate. We observe spectral
features of straight chains containing from 8 to 24 atoms. Low temperature PL
spectra reveal characteristic triplet fine-structures that repeat themselves
for carbon chains of different lengths. The triplet is invariably composed of a
sharp intense peak accompanied by two broader satellites situated 15 and 40 meV
below the main peak. We interpret these resonances as an edge-state neutral
exciton, positively and negatively charged trions, respectively. The
time-resolved PL shows that the radiative lifetime of the observed
quasiparticles is about 1 ns, and it increases with the increase of the length
of the chain. At high temperatures a non-radiative exciton decay channel
appears due to the thermal hopping of carriers between parallel carbon chains.
Excitons in carbon chains possess large oscillator strengths and extremely low
inhomogeneous broadenings.
