Our new starburst models consist of a standard dynamical model of the bubble/shell structure around a young star cluster, a time-dependent stellar population-synthesis model, a fully time-dependent chemistry model for the photo-dissociation regions, and a one-dimensional non-LTE line radiative-transfer model. Few previous models, if any, have all these physical elements included at the same time. This work pioneers a basic understanding of a few challenging and important issues and hopes to provide some potential answers to these questions. They are (1) Can we follow the evolution of an ensemble of GMCs and the swept-up shells, and model the FIR/submm/mm line emission in the ISM of a starburst galaxy? (2) Can we use these line emissions from giant molecular cloud fossils (the shells) to date the starburst? and (3) Are the ages predicted from our studies consistent with those measured from the use of red supergiant spectral features, or the absorption/emission spectral properties of dust in H II regions?

Finally, the predictions made by our theoretical modeling are useful for the interpretation of future ALMA high resolution maps of molecular gas on small and large scales in starburst galaxies, in order to provide a deeper understanding of the structure, dynamics, and evolution of the neutral ISM and its relationship with active star formation.