Overview of the physical properties characterising the reactions between He⁺ and NH₃, ND₃, N₂, CH₄ and CD₄ investigated in the current article series, and the calculated capture (k_calc), measured (k_obs) and estimated (k_est) thermal rate coefficients at several selected low temperatures relevant for astrophysics.

	NH3		ND3	N2		CH4	CD4
k L (10−15 m3 s−1)	1.887		1.860	1.637		2.048	2.006
k obs (10−15 m3 s−1)	4.5 (T = 27 K)64 3.0 (T = 68 K)64		—	1.2a (T = 8 K)10 1.3a (T = 20 K)10		1.26 (T = 300 K)41	—
k calc (10−15 m3 s−1)	11.3 (T = 27 K)b 29 7.39 (T = 68 K)b 29		—	2.06 (T = 8 K)32 1.98 (T = 20 K)32		2.048 (all  T)c	2.006 (all  T)c
k est (10−15 m3 s−1)	9.38 (0.16) (T = 3 K)b 6.67 (0.12) (T = 10 K)b		—	1.28(0.10) (T = 3, 10 K)		1.25 (all  T)	0.762 (all  T)
	9.83 (0.17) (T = 3 K)d 7.76 (0.14) (T = 10 K)d		—
Estimated percentage of reactive collisions	40%	41%	—	58 ± 17%	66 ± 20%	61%	37%
Reduced mass μ (u)	3.241		3.336	3.502		3.203	3.337
Polarizability volume α′ (10−30 m3)	2.103 (ref. 65)			1.710 (ref. 65)		2.448 (ref. 65)
Rotational constants (cm−1)	9.444 (ref. 66)		5.143 (ref. 67)	1.990 (ref. 68)		5.241 (ref. 58)	2.591 (ref. 59)
	6.196 (ref. 66)		3.125 (ref. 67)
Leading multipole moment	Dipole			Quadrupole		Octupole
	4.91 × 10−30 C m (ref. 69)			−4.65 × 10−40 C m2 (ref. 60)		7.41 × 10−50 C m3 (ref. 33)

^aExperimental uncertainty of ±30%.

^bAssuming nuclear-spin conservation.

^cCurrent article.

^dAssuming nuclear-spin relaxation.