The shape of the unidentified infra-red bands: analytical fit to ISOCAM spectra
F. Boulanger, P. Boisssel, D. Cesarsky, C. Ryter;
AaA, 1998, 339, 194
ABSTRACT:Modelling the unidentified infrared dust bands at 6.2 7.7, 8.6, 11.3, and 12.7 mum by Lorentz profiles is shown to produce excellent fits to the
spectra obtained with the Continuous Variable Filter (CVF) of the instrument
ISOCAM, on-board the Infrared Space Observatory (ISO).
The feature
pedestals are accounted for by the wide wings of the Lorentz curves which also
account for a large fraction of the 10 mum ``continuum".
The Lorentz shape of
the features is believed to reveal intrinsic properties of the emitters,
i.e.
a very short life time of the excited state, of the order of a few 10(-13)
s.
This is attributed to internal vibrational redistribution (IVR) between
thermally accessible modes of the particles, which can be raised at high
temperature by absorption of a single photon.
Particles of a few hundred atoms may
meet both requirements.
KEYWORDS: ism: clouds, ism: rho-ophiuchi cloud, ism: ngc 7023, infrared: ism: lines and bands, infrared: line formation
PERSOKEY:dust, pah, mir, iso, ,
CODE: boulanger98