Ultrafast decay of $E_{22}$ subband excitons in semiconducting SWNTs

We use CW and time-resolved spectroscopy for an investigation of intra- and interband relaxation of excited states in micelle suspended SWNTs. We observe that the dynamics of $E_{22}$ subband exciton decay in SWNTs is surprisingly similar to the dynamics of photoexcited carriers in bulk graphite. Moreover we find a clear correlation of the $E_{22}$ exciton decay rate with the excited state energy. We compare these results with earlier theoretical studies of quasi-particle decay in graphite and discuss the role of electron-electron and electron-phonon coupling for the dynamics of higher excited states.