The UMIST database for astrochemistry 1999

We report a new version of the UMIST database for astrochemistry. The previ ous (1995) version has been updated and its format has been revised. The da tabase contains the rate coefficients, temperature ranges and - where avail able - the temperature dependence of 4113 gas-phase reactions important in astrophysical environments. The data involve 396 species and 12 elements. W e have also tabulated permanent electric dipole moments of the neutral spec ies and heats of formation. A new table lists the photo process cross secti ons (ionisation, dissociation, fragmentation) for a few species for which t hese quantities have been measured. Data for Deuterium fractionation are gi ven in a separate table. Finally, a new online Java applet for data extract ion has been created and its use is explained in detail. The detailed new d atafiles and associated software are available on the World Wide Web at htt p://www.rate99.co.uk.