Current status of the H2 diffuse interstellar bands theory Assignments of the λλ5780, 6284, 4428, 4882 large-equivalent-width diffuse interstellar bands
Abstract
Major changes recently incorporated into the structure of the non-linear H2 DIBs model (P. P. Sorokin and J. H. Glownia, Astrophys J., 1996, 473, 900) are outlined. To account for observed relative intensities of narrow DIBs assigned in the original model to H2 inter-Rydberg transitions, it has become necessary to postulate a form of lightwave coherence existing in the H2-containing cloud of the model, with numerous coherent 2n wave-mixing processes, each initiated by broadband stimulated Raman scattering (SRS), occurring on various H2 transitions. By considering such wave-mixing processes, it becomes possible both to interpret archived VUV spectra of B-type supergiants and to easily assign large-equivalent-width DIBs (e.g. λλ5780, 6284, 4428, 4882) whose origins cannot be understood using the original 'passive' H2 two-photon absorption model. The wave-mixing schemes discussed also enable one to understand why DIB intensities in given lines-of-sight correlate well with the amount of reddening observed in the same lines-of-sight.