  Stellar nuclear fusion reactions take place in a hot, dense plasma within
stars. To account for the effect of these environments, the theory of open
quantum systems is used to conduct pioneering studies of thermal and atomic
effects on fusion probability at a broad range of temperatures and densities.
Since low-lying excited states are more likely to be populated at stellar
temperatures and increase nuclear plasma interaction rates, a 188Os nucleus was
used as a target that interacts with an inert 16O projectile. Key results
showed thermal effects yield an average increase in fusion probability of 15.5%
and 36.9% for our test nuclei at temperatures of 0.1 and 0.5 MeV respectively,
compared to calculations at zero temperature. Thermal effects could be tested
in a laboratory using targets prepared in excited states as envisaged in
facilities exploiting laser-nucleus interactions.
