The dynamics of evaporation from a liquid surface

► Recorded nascent rotational and vibrational spectra of molecules spontaneously evaporating. ► Rotations are cooled significantly more than the lowest-energy vibrational modes. ► Rotational energy distributions are Boltzmann, T(rot) = 200-230 K. ► Vibrational analysis indicates liquid surface temperature of 260-270 K. ► During phase transition, equivalent of 150-260 hard sphere collisions occur.