Table 1.
X-ray photodesorption yields at 564 eV of simple molecules from pure methanol ice (from Paper I) and 13CO:CH3OH and H2O:CH3OH mixtures, at 15 K and for a dose between 5 × 1015 and 2 × 1016 photon cm−2.
| Photodesorption yields in 10−3 molecule/photon | 13CO:CH3OH ice |
H2O:CH3OH ice |
|||
|---|---|---|---|---|---|
| Mass – photodesorbed species | Pure CH3OH | 1:1 | 6:1 | 1.5:1 | 3:1 |
| 15 – CH3 (3) | 1.3±0.2 | 3.0±0.3 | 7.1±0.7 | 1.8±0.2 | 3.0±0.3 |
| 16 – CH4, O,13CH3 | 1.1±0.2 | 3.8±0.5 | 15±2 | 1.4±0.2 | 2.0±0.3 |
| 17 – OH, 13CH4 (1) | ND ( * *) | 1.7±0.7 | 7.9±3.2 | ND ( * *) | ND ( * *) |
| 18 – H2O | 7.5±1.1 | NM ( * ) | NM ( * ) | 3.4±0.4 | 2.3±0.4 |
| 28 – CO | (1.2)±0.1 × 102 | (1.7)±0.1 × 102 | (8.4)±0.2 × 102 | 46±2 | 86±4 |
| 29 – HCO, 13CO | NM ( * ) | (2.5)±0.1 × 102 | (4.4)±0.2 × 102 | 16±1 | 83±4 |
| 31 – CH2OH, CH3O | ND (2) | ND (2) | ND (2) | 1.3±0.3 | 5.2±1.0 |
| 44 – CO2 | 24±1 | 85±4 | (2.6)±0.2 × 102 | 77±4 | 97±5 |
| 45 – 13CO2 | 52±3 | 80±4 | |||
Notes. As explained in Sect. 3.2, these yields were corrected for the dilution factor of the corresponding parent molecule for 13CO:CH3OH and H2O:CH3OH ices. ( * )NM = Not measured: we did not measure the corresponding mass in the QMS for the ice considered ( * *)ND = Not detected: the desorption signal measured for the considered species is below our signal-to-noise ratio, meaning that we did not detect its desorption from the ice. Considering the noise profile on the mass channel 17 of our QMS, if OH photodesorption occurs, the photodesorption yield is < 5 × 10−4 molecule/photon. (1)For 13CO:CH3OH mixtures only. The values given for the mass 17 are given without being able to correct from the cracking of possible photodesorbed H2O into OH in the QMS. Thus these values may be overestimated. (2)We assumed that the desorption of CH2OH and/or CH3O from pure methanol ice and 13CO:CH3OH mixtures is negligible. (3)These yields are given without being able to correct from the cracking of CH4 into CH3 in the QMS. Thus these values may be overestimated.
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