CCCBDB listing of experimental data page 2

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Property	Value	Uncertainty	units	Reference
Hfg(298.15K)	391.20	1.60	kJ mol^-1	2005Rus/Bog:573
Hfg(0K)	390.70	1.60	kJ mol^-1	2005Rus/Bog:573
Entropy (298.15K)	194.44		J K^-1 mol^-1	2005Rus/Bog:573
Integrated Heat Capacity (0 to 298.15K)	10.03		kJ mol^-1	2005Rus/Bog:573
Heat Capacity (298.15K)	35.13		J K^-1 mol^-1	2005Rus/Bog:573

Mode Number	Symmetry	Frequency			Intensity			Comment	Description
Mode Number	Symmetry	Fundamental(cm^-1)	Harmonic(cm^-1)	Reference	(km mol^-1)	unc.	Reference	Comment	Description
1	A₁	2806		1999Das/Whi:175					CH₂ s-stretch
2	A₁	963		VEEL5					CH₂ bend
3	B₂	3190		VEEL5					CH₂ a-stretch

Description	Value	unc.	Connectivity				Reference	Comment
Description	Value	unc.	Atom 1	Atom 2	Atom 3	Atom 4	Reference	Comment
rCH	1.085		1	2			1998Kuc	r0 value
aHCH	135.5		2	1	3		1998Kuc	a0 value

Atom	y (Å)	z (Å)
C1	0.0000	0.1027
H2	1.0042	-0.3081
H3	-1.0042	-0.3081

	C1	H2	H3
C1		1.0850	1.0850
H2	1.0850		2.0084
H3	1.0850	2.0084

	Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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State	Config	State description	Conf description	Exp. min.	Dipole (Debye)				Reference	comment	Point Group	Components
State	Config	State description	Conf description	Exp. min.	x	y	z	total	Reference	comment	Point Group	dipole	quadrupole
1	1	³B₁	C_2v	True							C_2v	1	2
1	2	³Σ_g	D_∞h	False							D_∞h	0	1
2	1	¹A₁	C_2v	True							C_2v	1	2

squib	reference	DOI
1982Sea/Bun:5348	Sears, T.J.; Jennings, D.A.; Brown, J.M. "The rotational spectrum and hyperfine structure of the methylene radical CH2 studied by far-infrared laser magnetic resonance spectroscopy." Journal of Chemical Physics. 77, 5348-5362 (1982)	10.1063/1.443783
1998Kuc	K Kuchitsu(ed) "Structure of Free Polyatomic Molecules - Basic Data" Springer, Berlin, 1998	10.1007/978-3-642-45748-7
1999Das/Whi:175	Das and Whittenburg. Performance of the hybrid density functionals in the determination of the geometric structure, vibrational frequency and singlet-triplet energy separation of CH2, CHF, CF2, CCl2 and CBr2. J. Mol. Struct. (Theochem). Vol. 492. pgs. 175-186.	10.1016/S0166-1280(99)00279-1
2005Rus/Bog:573	B Ruscic, JE Boggs, A Burcat, AG Csaszar, J Demaison, R Janoschek, JML Martin, ML Morton, MJ Rossi, JF Stanton, PG Szalay, PR Westmoreland, F Zabel, T Berces "IUPAC Critical Evaluation of Thermochemical Properties of Selected Radicals. Part I" J. Phys. Chem. Ref. Data, Vol. 34, No. 2, 2005, 573	10.1063/1.1724828
VEEL5	M.E. Jacox, Vibrational and Electronic Energy Levels of Polyatomic Transient Molecules, J. Phys. Chem.Ref. Data, Monograph 3 (1994) (updated data in NIST Chemistry Webbook - http://webbook.nist.gov/chemistry/
webbook	NIST Chemistry Webbook (http://webbook.nist.gov/chemistry)	10.18434/T4D303

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Experimental data for CH2+ (methylene cation)

Experimental data for CH₂⁺ (methylene cation)