Code used:
TROVE , version j-trove1809.x from 18 September 2016

See on GitHub and also the TROVE manual. 

INPUTS:

There were four main step inputs into TROVE, used to determine the line list for 12C2-1H4.

Step1: read externally produced curvilinear hamiltonian, save primitive and contracted basis functions, fast-ci matrix elements and vibrational component
of full hamiltonian.

Step2: save matrix elements of other components of hamiltonian (4 4 example here)

Step3: Make list of largest transition moment to each state for prunning procedure

Step4: Convert matrix elements to J=0 representation, save J=0 basis using transition moment prunning.

Implementation notes:

Twelve-dimensional (12D), ab initio electric dipole moment surfaces (DMSs) of ethylene in its ground electronic state were generated.
The DMS was computed using the CCSD(T)-F12b method in conjunction with an aug-cc-pvTZ-basis set and corresponding f12 auxilary basis sets.
A new spectroscopic PES was implemented. It was created as follows;an ab initio PES was generated employing
the CCSD(T)-F12b approach used for the DMSs, but with the cc-pVTZ-F12 basis set. The frozen core approximation was applied in the coupled cluster calculations.
Core-valence corrections and higher-order coupled cluster corrections were not included.

Vibrational basis set pruned via transition moment described in publication.