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Table 3
Critical density for transitions of interest.
| Transitions | Critical density (a) |
|---|---|
| (cm−3) | |
| CS 5-4 | 1.3 × 106 |
| CH3CCH 120–110 | 2.9 × 104 (b) |
| H2CS 60,6–50,5 | 2.2 × 105 |
| CH3OH 51,5–41,4 | 6.3 × 105 |
| CH3OH 54,5–44,4 | 5.3 × 107 |
| CH3CN 130–120 | 4.6 × 106 |
| CH3CCH 140–130 | 4.3 × 104 (b) |
| H2CS 70,7–60,6 | 3.7 × 105 |
| C2H N = 3–2, J = 7∕2–5/2, F = 4–3 | 2.7 × 105 |
| SO 45–34 | 2.2 × 105 |
| SO 66–55 | 7.0 × 105 |
| SO 76–65 | 1.0 × 106 |
| H13CO+ 3–2 | 9.5 × 105 |
| SO2 140,14–131,13 | 4.0 × 105 |
| SO2 32,2–21,1 | 1.7 × 105 |
| CH3CCH 150–140 | 5.7 × 104 (b) |
Notes. (a) Calculated following the definition in Shirley (2015) in the optically thin limit (τ ~ 0.1) at 50 K, considering a multi-level energy system whenever necessary. (b) Calculated using collisional coefficients of CH3CN.
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