0 Assigned ID: 620 ----- Attempting Submission 1 (Fri Apr 11 17:44:00 GMT 2014) ----- HST Phase I Proposal 620 (proposaltmp1.apt) successfully submitted. ----- Attempting Submission 2 (Fri Apr 11 21:29:27 GMT 2014) ----- The detailed understanding of the formation, destruction, and excitation of molecular hydrogen, H2, and its singly-deuterated isotopologue, HD, is crucial for astrophysical models of the postrecombination era, of local and extragalactic interstellar clouds, of circumstellar shells and protoplanetary disks, e.g. nearly every environment where molecular gas is exposed to UV irradiation resulting in a photodissociation region (PDR). However, the dominant impactors for exciting H2 and HD are para-H2 and ortho-H2. Rate coefficients for these colliders are limited to vibrational levels v<4 for H2 and v=0 for HD. Further, they are based on approximate calculations which treated the colliding H2 as a pseudo-atom. Here we propose to extend our full-dimensional 6D quantum calculations for H2-H2 with v=0-2 up to v=14 and to perform for the first time initial rovibrational calculations for HD-H2. The availability of the proposed rate coefficients will allow for advanced PDR models along site lines observed with STIS and motivate future COS observations. In a number of cases, a large number of absorption features (up to 300) have been observed allowing for detailed model refinement and potentially new PDR physics. The rate coefficients will be distributed to the astrophysical modeling community via standard database formats (e.g., LAMDA, BASECOL, Cloudy). ISM AND CIRCUMSTELLAR MATTER Default Small false false false false true SUPPORTED