Discovery of HC4NC in TMC-1: A study of the isomers of HC3N, HC5N, and HC7N

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Table C.1.

Energies, rotational constants, quadrupole coupling constants, dipole moment, and vibrational partition functions of the HC₅N isomers evaluated at MP2/cc-pVTZ level of theory.

	ΔE^(a)	ΔE_MP2^(b)	A₀^(c)	B₀^(c)	C₀^(c)	1.5χ_aa	0.25(χ_bb − χ_cc)	μ_T	Q_v^(d)	Q_v^(d)
	(kJ mol⁻¹)	(kJ mol⁻¹)	(MHz)	(MHz)	(MHz)	(MHz)	(MHz)	(D)	50 K	300 K
HC₅N ^(e)	0.0	0.0		1320.046		−5.77		4.36	1.09	22.89
HC₄NC ^(f)	134.7	133.8		1390.737		1.15		3.57	1.07	22.62
C₃CHCN	256.1	254.5	21076.776	1689.938	1564.496	−2.73	−0.41	3.09	1.10	14.18
C₅NH	269.2	267.7		1348.267		2.10	0.31	9.14	1.02	8.86
HC₂NC₃	294.1	292.2		1434.147		2.96		6.58	1.01	8.06
HC₂C(C)CN	289.3	284.2	10693.657	2526.651	2038.799	−4.72	−0.20	3.27	1.06	15.93
HC₃NC₂	320.8	316.2		1435.856		0.91		7.15	1.03	15.46
C₂CHC₂N	365.5	361.3	11195.360	2552.013	2073.245	−5.24	−0.14	4.48	1.15	15.16

Notes.

^(a)

Relative energy to the lowest energy isomer HC₅N evaluated at MP2/cc-pVTZ level of theory.

^(b)

Relative energy including the zero-point correction energy calculated for each species.

^(c)

Rotational constants at the ground state evaluated using the vibration-rotation interaction constants obtained using the anharmonic corrections. In the case of the quasi linear C₅NH, the effective rotational constant, B_eff, is provided.

^(d)

Vibrational partition function calculated using the expression ∏_i(1 − e^{−(hω_i/KT)})^−d_i (Gordy & Cook 1984), where ω_i and d_i represent the energy and the degeneracy of each i vibrational mode. The energies for the vibrational modes are taken from the results of ab initio calculations evaluated at MP2/cc-pVTZ level of theory, under the anharmonic correction. At the temperature of TMC1 (10 K), the vibrational partition function for isomers is equal to one.

^(e)

The experimental value is B₀ = 1331.33269 ± 0.00002 (Bizzocchi et al. 2004). The ratio B₀(exp)/B₀(Cal) is 1.0086.

^(f)

The experimental value is B₀ = 1401.18216 ± 0.00006 (this work, see Table A.3. The ratio B₀(exp)/B₀(Cal) is 1.0075.

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