Table A.1: Initial gas-phase and total abundances.

Species	x(i) T > 100 K	x(i) T < 100 K	x(i) total
CO	1.8E-04a	1.8E-04a
CO2	1.5E-05b	0.00f
H2O	7.5E-05c	0.00f
H2S	8.0E-07d	0.00f
N2	3.5E-05e	3.5E-05e
CH4	5.0E-08e	5.0E-08e
C2H4	4.0E-08e	4.0E-08e
C2H6	5.0E-09e	5.0E-09e
H2CO	6.0E-08e	0.00f
CH3OH	5.0E-07e	0.00f
He	8.5E-02h	8.5E-02h	8.5E-02h
C	1.0E-08h	1.0E-08h	3.5E-04i
N	1.0E-08h	1.0E-08h	1.1E-04i
O	0.00e	4.0E-05g	4.5E-04i
S	0.00e	3.0E-09d	1.0E-05i
Si	1.0E-08h	1.0E-08h	3.5E-05i
Cl	1.0E-08h	1.0E-08h	9.3E-08i
Fe	1.0E-08e	1.0E-08e	3.2E-05i
Ne	1.0E-08h	1.0E-08h	1.4E-04i
Na	1.0E-08h	1.0E-08h	2.1E-06i
Mg	1.0E-08h	1.0E-08h	4.0E-05i
Al	1.0E-08h	1.0E-08h	3.1E-06i
Ar	1.0E-08h	1.0E-08h	3.8E-06i
Ca	1.0E-08h	1.0E-08h	2.3E-06i
Cr	1.0E-08h	1.0E-08h	5.0E-07i
Ni	1.0E-08h	1.0E-08h	1.8E-06i

All abundances are relative to total hydrogen. Only the abundances in the 2. and 3. column enter the chemistry. The total abundances x(i) (4. column) are for the attenuation of the X-rays. a van der Tak et al. (1999), b Boonman et al. (2003b), c Boonman & van Dishoeck (2003), d see text, e Charnley (1997), f assumed to be frozen-out or absent in cold gas-phase, g taken to be consistent with Meyer et al. (1998), h assumed abundances, i Yan (1997).