Table 1
FTS molecular transitions.
| Molecule | Transition | Frequency | HPBWa | EU b | ρcrit c |
| (GHz) | (arcsec) | (K) | (cm-3) | ||
|
|
|||||
| Ud | − | 80.5599 | 30.5 | − | − |
| HC3N | (9−8) | 81.8816 | 30.0 | 19.6 | 4.2 × 105 |
| C3H2 | (20,2−11,1) | 82.0935 | 30.0 | 6.4 | − |
| C3H2 | (21,2−10,1) | 85.3388 | 28.8 | 6.4 | − |
| C4H | (9 −8, J = 17/2−15/2) | 85.6725 | 28.7 | 4.1 | − |
| NH2D | (11,1−10,1) | 85.9262 | 28.6 | 20.7 | − |
| H13CN | (1−0) | 86.3399 | 28.5 | 4.1 | 2.0 × 106 |
| HCN | (1−0) | 88.6318 | 27.8 | 4.2 | 2.2 × 106 |
| HCO+ | (1−0) | 89.1885 | 27.6 | 4.3 | 1.6 × 105 |
| HNC | (1−0) | 90.6635 | 27.1 | 4.4 | 2.8 × 105 |
| N2H+ | (1−0) | 93.1734 | 26.4 | 4.5 | 1.4 × 105 |
| C34S | (2−1) | 96.4129 | 25.5 | 6.2 | − |
| CH3OH | (2− 1,2−1− 1,1) | 96.7393 | 25.4 | 12.5 | − |
| CH3OH | (20,2−10,1) | 96.7413 | 25.4 | 7.0 | − |
| 34SO | (32−21) | 97.7153 | 25.2 | 9.1 | − |
| CS | (2−1) | 97.9809 | 25.1 | 7.1 | 3.3 × 105 |
| SO | (32−21) | 99.2998 | 24.8 | 9.2 | − |
| HC3N | (11−10) | 100.076 | 24.6 | 28.8 | 8.8 × 105 |
| C18O | (1−0) | 109.7821 | 22.3 | 5.3 | 1.9 × 103 |
| Ud | − | 109.9531 | 22.4 | − | − |
| 13CO | (1−0) | 110.2013 | 22.3 | 5.3 | 1.9 × 103 |
Notes.
ρcrit = Aul/γ, where Aul is the Einstein spontaneous emission coefficient and γ = σ ⟨ v ⟩ is the collisional rate where σ is the cross section of the collision for each transition and ⟨ v ⟩ ≈ (3kT/m)1/2 is the average velocity of the collisional particles. As H2 is the most abundant molecule it is used as the dominant collisional particle. We assume T = 10 K. The Einstein spontaneous emission coefficients and γ values are taken from LAMDA database (http://home.strw.leidenuniv.nl/~moldata/).
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