(Tennyson et al. 2017).
4 The cross-sections for excitation to the first vibrationally
excited level are around two orders of magnitude smaller (see also Faure and Josselin
2008) than this as shown by the example for CO excitation from the v ¼ 0 to v ¼ 1
Fig. 3.12 Calculations of the radiance of H 2 O at two different gas temperatures for weak cometary
activity (optical depth ¼ 0) using the Planetary Spectrum Generator (Villanueva et al. 2018). The
plot at 70K has been offset vertically to allow ease of comparison
Fig. 3.13 Solid line: VIRTIS-H observation of water vapour above the limb of 67P from the
summation of 21 observations between 24 Dec 2014 and 25 Jan 2015. Dashed line: Model of the
emission obtained using the Planetary Spectrum Generator (Villanueva et al. 2018) with a column
density of 5 10
19 m
À2 at a temperature of 100 K. A heliocentric distance of 2.6 AU was assumed.
The calculation was made at 1.1 nm resolution and subsequently degraded to 3.3 nm by smoothing
4 https://www.quantemoldb.com Note that some services on this site are commercial.
202
3 Gas Emissions Near the Nucleus
4 The cross-sections for excitation to the first vibrationally
excited level are around two orders of magnitude smaller (see also Faure and Josselin
2008) than this as shown by the example for CO excitation from the v ¼ 0 to v ¼ 1
Fig. 3.12 Calculations of the radiance of H 2 O at two different gas temperatures for weak cometary
activity (optical depth ¼ 0) using the Planetary Spectrum Generator (Villanueva et al. 2018). The
plot at 70K has been offset vertically to allow ease of comparison
Fig. 3.13 Solid line: VIRTIS-H observation of water vapour above the limb of 67P from the
summation of 21 observations between 24 Dec 2014 and 25 Jan 2015. Dashed line: Model of the
emission obtained using the Planetary Spectrum Generator (Villanueva et al. 2018) with a column
density of 5 10
19 m
À2 at a temperature of 100 K. A heliocentric distance of 2.6 AU was assumed.
The calculation was made at 1.1 nm resolution and subsequently degraded to 3.3 nm by smoothing
4 https://www.quantemoldb.com Note that some services on this site are commercial.
202
3 Gas Emissions Near the Nucleus