To date, over 100 molecules have been detected in interstellar and
circumstellar regions (Table 1), and detailed models of chemical synthesis
have been developed for dark clouds (Hasegawa & Herbst
1993; Herbst et al.
1994; Bergin et al. 1995; Neufeld et al.
1995; Mackay 1996), hot molecular cores
(Charnley et al. 1992; Charnley et al. 1995;
MacKay 1995), circumstellar envelopes
(Cherchneff et al. 1993; Cherchneff &
Glassgold 1993; Millar
& Herbst 1994), and Photon-Dominated Regions
(Sternberg & Dalgarno 1995).
Many of these have used data from previous releases of the UMIST database
(Millar et al. 1991b; Farquhar & Millar 1993), as have modellers of comet
chemistry (Eberhardt et al. 1994; , Meier et al.
1993, 1994; Eberhardt &
Krankowsky 1995; Altwegg et al. 1994). In this paper, we report
on our latest release of the UMIST database which has been extended to
include rate coefficients on 3864 reactions among 395 species and 12 elements
with neutral molecules containing up to 12 atoms (
) and represents
an increase of around one-third on the 1990 version (Millar et al. 1991b).
Section 2 contains a summary of the information contained in the species file and on related information such as electric dipole moments and heats of formation. Section 3 presents the rate coefficients and discusses the important changes made for this update, while Sect. 4 contains the results of a time-dependent calculation of a dense cloud model. Finally, Sect. 5 describes how the data may be obtained.
Table 1: Observed interstellar and circumstellar molecules as
of December 1995