• Witt, Adolf
• Vijh, Uma
• Gordon, Karl

Abstract

Interstellar dust grains are known sources of photoluminescence (PL), which is excited by absorption of UV photons. Previous investigations of this phenomenon have focused upon PL in the red part (540-950 nm) of the spectrum, and is known as Extended Red Emission (ERE). Many models have been proposed to account for ERE such as hydrogenated amorphous carbon (HAC), polycyclic aromatic hydrocarbon (PAH) clusters, coal or Carbon nanoparticles and Silicon nanoparticles. Most of these models predict additional PL in spectral regions other than the ERE range. In particular, the hydrogen-passivated Si nanoparticle model and the small PAH (atomic mass < 500 a.m.u.) model predict PL in the near-UV and blue part of the spectrum. We present results from our sensitive search for this predicted blue-PL. We have obtained long-slit, low-resolution spectra of a number of reflection nebulae, where presence of ERE has been established. Our technique involves the comparison of the equivalent widths of the Hydrogen-Balmer lines in the nebular and the stellar spectra. Presence of continuous PL will manifest itself by the reflected lines in the nebular spectrum having a smaller equivalent width. Our results impose upper limits on the presence of PL shortward of 500 nm and constrain the present models for luminescent interstellar dust particles.

Topics

• nanoparticle
• impedance spectroscopy
• photoluminescence
• cluster
• amorphous
• Carbon
• grain
• Hydrogen
• Silicon