Cooling dynamics of photo-excited negative carbon cluster ions stored in an ion storage ring

A newly found fast radiative cooling process of C6- is studied by simulation based on statistical sharing of the internal energy by the vibrational modes both in the electronic ground and excited states. For comparison, a contrasting slow cooling of C6H− is simulated by the same procedure. The simulation demonstrates a distinct difference in the time evolution of energy distributions between C6- and C6H−, and well reproduces the observed fast cooling of C6- by recurrent electronic transitions and the slow cooling of C6H− by vibrational de-excitation.