Notes. ^(a) Q_r is the rotational partition function (without taking the hyperfine splitting into account). We took J = 250 as the maximum value, where the centrifugal distortion (up to the sextic terms) was taken into account to calculate the partition function within a semirigid rotor approximation. A complete set of the calculated B2PLYPD3/aug-cc-pVTZ centrifugal distortion constants (Watson’s S-reduction in the I^r representation) is given in Table A.1. ^(b) Q_v is the vibrational partition function. The total partition function of the molecule without hyperfine splitting is Q_r × Q_v. However, for predictions including the hyperfine structure, the total partition function should be multiplied by the nuclear spin statics contribution (in this case, Q_n = 9 due to the two nitrogen nuclei).