Abstract
Fullerene C60 has been confirmed as an interstellar molecule since its infrared (IR) emission bands were identified
in spectra of a young planetary nebula, namely Tc 1, in 2010, by observation using a space telescope of Spitzer/IRS. In order to provide experimental and theoretical backgrounds needed for estimation of vibrational temperature and molecular abundance in space, IR emission spectra of C60 thin films were measured in the laboratory and temperature dependence of the IR emission intensity was examined experimentally for four IR-active T1u modes of C60. Based on spontaneous emission from thermally populated vibrationally excited levels in a C60 molecule, theoretical simulations were performed on IR emission intensity at elevated temperatures. Thereby, it was clarified how and why the IR emission spectra change by different temperatures. Depending on the vibrational-mode frequencies, temperature dependence of the IR-emission intensity differs, thus relative intensity of these IR-emission bands can be exploited as thermometer of vibrational temperature for far distant molecules.
https://ror.org/05kt9ap64 
