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Table 2

Rotational partition function for the symmetric and asymmetric conformers of mono-deuterated DME in the ground vibrational state computed for nine different temperatures.

Temperature 2.275 K 5 K 9.375 K 18.75 K 37.5 K 75 K 150 K 225 K 300 K

Symmetric conformer
A state 58.6 142.5 361.4 1015.2 2861.7 8082.2 22 850.4 41 941.2 64 256.6
E state 58.6 142.5 361.4 1015.2 2861.7 8082.2 22 850.4 41 941.2 64 256.6
Total 117.2 285.0 722.8 2030.4 5723.5 16 164.3 45 700.8 a 83 882.3b 128 513.1b
Approx.c 111.7 277.6 712.8 2016.0 5702.2 16 164.3 45 617.5 83 804.6 129 025.6
Ratio 1.049 1.027 1.014 1.007 1.004 1.002 1.002 1.001 0.996
Asymmetric conformer
A state 119.2 289.6 734.2 2061.8 5811.8 16 413.5 46 407.7 85 201.7 130 629.7
E state 119.1 289.5 734.1 2061.8 5811.8 16 413.5 46 407.7 85 201.7 130 629.7
Total 238.3 579.1 1468.3 4123.7 11 623.5 32 826.9 92 815.4a 170 403.4b 261 259.3b
Approx.c 226.8 563.7 1447.4 4093.7 11 578.8 32 749.9 92 630.6 170 173.4 261 999.0
Ratio 1.051 1.027 1.014 1.007 1.004 1.002 1.002 1.001 0.997

Notes. The data presented in bold are the results used for the astrophysical detection in Sect. 7. This table is given for the rotational degrees of freedom; the contributions from vibrational excited states are ignored.

(a)

The sum of states did not converge completely, error for total  < 20 for the symmetric conformation,  < 40 for asymmetric.

(b)

The sum of states has not converged (this is the reason for ratio  < 1 at 300 K).

(c)

These values are computed with the rigid asymmetric rotor approximation.

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