title: Titanium carbide nanocrystals in circumstellar environments.
abstract: Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that infrared wavelength spectra of gas-phase titanium carbide nanocrystals derived in the laboratory show a prominent feature at a wavelength of 20.1 micrometers, which compares well to a similar feature in observed spectra of postasymptotic giant branch stars. It is concluded that titanium carbide forms during a short (approximately 100 years) phase of catastrophic mass loss (>0.001 solar masses per year) in dying, low-mass stars.
authors.affiliation: FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, NL-3430 BE Nieuwegein, Netherlands. gertvh@rijnh.nl
authors.forename: G
authors.initials: G
authors.lastname: von Helden
authors.forename: A G
authors.initials: AG
authors.lastname: Tielens
authors.forename: D
authors.initials: D
authors.lastname: van Heijnsbergen
authors.forename: M A
authors.initials: MA
authors.lastname: Duncan
authors.forename: S
authors.initials: S
authors.lastname: Hony
authors.forename: L B
authors.initials: LB
authors.lastname: Waters
authors.forename: G
authors.initials: G
authors.lastname: Meijer
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D019443:Cosmic Dust; D014025:Titanium
chemical_list: D019443:Cosmic Dust; C096521:titanium carbide; D014025:Titanium