**Table 2:** Initial abundances at t=0 relative to H₂ for AFGL 2591.
Species	Initial abundance	Ref.
Initial abundance ( $T>100~{\rm K}$ )
CO	3.7(-4)	a
CO₂	3.0(-5)	d
H₂O	1.5(-4)	d
H₂S	1.6(-6)	h
N₂	7.0(-5)	e
CH₄	1.0(-7)	e
C₂H₄	8.0(-8)	e
C₂H₆	1.0(-8)	e
O	0.0(0)	e
H₂CO	1.2(-7)	e
CH₃OH	1.0(-6)	e
S	0.0(0)	e
Fe	2.0(-8)	e
Initial abundance ( $T<100~{\rm K}$ )
CO	3.7(-4)	a
CO₂	0.0(0)	f
H₂O	0.0(0)	f
H₂S	0.0(0)	f
N₂	7.0(-5)	e
CH₄	1.0(-7)	e
C₂H₄	8.0(-8)	e
C₂H₆	1.0(-8)	e
O	8.0(-5)	g
H₂CO	0.0(0)	f
CH₃OH	0.0(0)	f
S	6.0(-9)	h
Fe	2.0(-8)	e

$^{{\rm }}$ a(b) means $a \times 10^{b}$ .
$^{{\rm }}$ All abundances are gas-phase, and relative to H₂.
$^{{\rm a}}$ van der Tak et al. (1999); $^{{\rm b}}$ van der Tak et al. (2000); $^{{\rm c}}$ van der Tak & van Dishoeck (2000); $^{{\rm d}}$ Boonman et al. (2000); $^{{\rm e}}$ Charnley (1997); $^{{\rm f}}$ assumed frozen-out or absent in cold gas-phase, $^{{\rm g}}$ taken to be $\sim$ consistent with Meyer et al. (1998); $^{{\rm h}}$ Doty et al. (2002).

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