Open Access
Table 1
Symbols and abbreviations used repeatedly.
| Abbreviation | Description | Example unit |
|---|---|---|
| Physical parameters in the gas parcel | ||
| t | Simulation integration time | yr, s |
| Tgas | Gas temperature | K |
| NH | Hydrogen atom column density | cm−2 |
| NH | Hydrogen atom number density | cm−3 |
| n(H2) | Hydrogen molecule number density | cm−3 |
| ζ | Cosmic-ray ionisation rate | s−1 |
| Granular parameters | ||
| ng | Number density of interstellar grains | cm−3 |
| Td | Dust grain temperature | K |
| a | Dust grain radius | μm |
| b | Ice mantle thickness on grains | μm, MLs |
| X:H2O | Icy species’ X abundance relative to that of water ice | % |
| ML | Monolayer –ice layer with the thickness of a single molecule | |
| Desorption energy parameters | ||
| ED | Surface molecule desorption (binding) energy | K |
| Ediff | Surface molecule diffusion energy; 0.5ED | K |
| ED,pol | Default base ED value, on H2O ice surface | K |
| ED,np | ED on hyper-volatile (CO) ice surface | K |
| ED,bare | ED for molecules on completely bare grains | K |
| ED,np/ED,pol | Factor for ED,pol change in CO ices | |
| ED,pol-ED,bare | Energy value of a H-bond. | K |
| EA | Reaction activation energy | K |
| Xdes | Fitting parameter for ED on mixed ice, Eq. (3) | |
| H-bond rule | Bare grain surface does not form hydrogen bonds. | |
| Hyper-volatiles | Icy species with ED lower than ≈1300 K | |
| Efficiency parameters for desorption mechanisms | ||
| fCRD | Frequency of cosmic-ray induced heating of whole grains | s−1 |
| Ypd | UV photodesorption yield. | molecule photon−1 |
| fCD | Probability for surface reaction product desorption | |
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