aoforce supports the generation of input files for the hotFCHT code (version 2.0 and later) of R. Berger and co-workers, see hotFCHT, which allows for the calculation of Franck-Condon factors. Just include the keyword $hotfcht in the control file. The option is also active in analysis mode, that is as long as you still have the data group $hessian (in the control file or in a file referenced in the control file) you can always use aoforce (in analysis mode) to quickly generate the hotFCHT input. The program will write three files. The first one, hotfcht_header.inp contains a collection of the most important keywords of hotFCHT (set to some default values, please adapt to your needs) and list of all atomic masses (either TURBOMOLE’s default masses or the ones given in the $atoms data group). The other two, hotfcht_data_i.inp and hotfcht_data_f.inp contain the vibrational frequencies, normal modes and the names of the irreducible representations of the normal modes. In the former file, these data are associated with the hotFCHT keywords for the initial state, while the latter file contains the same data, but associated with the keywords for the final state. In order to run a hotFCHT calculation, you need to optimize the structures of two electronic states (usually the electronic ground state and an excited or ionized state) and obtain the harmonic force fields for both, using either aoforce or NumForce. In order to generate the hotFCHT input, just concatenate the hotfcht_header.inp file (from any of the two calculations) and the hotfcht_data_i.inp file from the calculation that refers to the initial state (e.g. the ground state in case of an absorption spectrum) and the hotfcht_data_f.inp file from the calcuation of the final state (the excited state in case of an absorption spectrum). Carefully edit the keywords in the header of the resultant file and run hotFCHT (please, refer to the hotFCHT documentation for further information).