NIST Hydrocarbon C5H4 tables

C₅H₄ - Pentadiyne

Rotational and centrifugal distortion constants for 1,4-pentadiyne
Parameter	CH₂(CCH)₂ Ground State	CH₂(CCH)₂ ν₂₁ = 1	CH₂(CCD)₂ Ground State	Ref.
A″ [MHz]	19 076.77(2) ^a	19 300.82(11)	17 408.3(112)	81036
B″ [MHz]	2859.224(3)	2870.209(2)	2574.372(13)
C″ [MHz]	2520.801(3)	2524.646(5)	2270.134(13)
τ₁ [MHz]	0.2392(1)	0.2379(90)	0.2012(63)
τ₂ [MHz]	0.021 82(1)	0.024 91(38)	0.0207(89)
τ₃ ^b [MHz]	0.6068(11)	1.58(90)	1.25(220)
τ_aaaa [MHz]	-2.963(3)	-10.2(45)	-17.5(450)
τ_bbbb [MHz]	-0.011 38(1)	-0.1296(146)	-0.010 59(171)
τ_cccc [MHz]	-0.003 17(2)	-0.003 94(83)	-0.003 16(57)

^a Uncertainties are one standard deviation.

^b Value determined by setting R₆ = 0.

C₅H₄ - Methyl Diacetylene

Molecular constants for methyl diacetylene (1,3-pentadiyne) and deuterated isotopic species in the ground state
Parameter	CH₃C₄H	Ref.	CH₃C₄D	CD₃C₄H	CD₃C₄D	Ref.
B₀ [MHz]	2035.747 06(8)	84035	1929.772(30)	1834.856(20)	1742.214(20)	55019
D_JK [kHz]	19.8630(13)		18.3(1)	14.5(1)	13.5(1)
D_J [kHz]	0.086 687(40)		0.06	0.1	0.1
H_KJ [Hz]	0.3278(37)
H_JK [Hz]	0.035 68(21)
H_J [Hz]	0.000 0130(66)
Dipole Moment
µ_a [C · m] µ_a [D]	4.0265(33) x 10^-30 1.2071(10)	84035

Molecular constants for methyl diacetylene (1,3-pentadiyne) and deuterated isotopic species in the ground state ^a
Species	υ	B_υ [MHz]	q [MHz]	D_JK [kHz]	ζ	X ^b [kHz]	Ref.
CH₃C₄H	1	2040.14(2)	2.104	20.0	0.9	0.15	55019
CH₃C₄D	1	1933.86(2)	1.956	18.7	0.92	0.20
CD₃C₄H	1	1838.69(2)	1.804	14.6	0.9	0.23
CD₃C₄D	1	1745.80(2)	1.684	14.0	0.9	0.23
¹³CH₃C₄H	0	1982.68(4)					57017
CH₃¹³CC₃H	0	2025.31(4)
CH₃C₃¹³CH	0	2018.96(4)
CH₃C₂¹³CCH	0	1980.22(4)
¹³CH₃C₄D	0	1879.93(4)
CH₃¹³CC₃D	0	1919.42(4)
CH₃C₂¹³CCD	0	1915.84(4)
CH₃C₃¹³CD	0	1881.88(4)

^a From [55019].

^b From X = q²/4 [(1-ζ) A_υ - B_υ].

NIST Physical Measurement Laboratory