Magnesium monohydride

Formula: HMg
Molecular weight: 25.3129
IUPAC Standard InChI: InChI=1S/Mg.H
IUPAC Standard InChIKey: RZCHRULKKYOSQS-UHFFFAOYSA-N
CAS Registry Number: 14332-53-7
Chemical structure:
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Constants of diatomic molecules

Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through March, 1977

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for ²⁴MgH
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
Unidentified line structure at 42570 cm^-1 [em. and abs., Guntsch, 1934 Guntsch, 1935 Turner and Harris, 1937 Guntsch, 1939] and 43180 - 43520 cm^-1 [abs., Khan, 1962].
I (²Π)					[5.96]			[2E-4]		[1.71₀]	I ← X V	47997.₆ Z
I (²Π)	↳Khan, 1962
H (²Σ⁺) 1											H ← X R	47543 (Z)
H (²Σ⁺) 1	↳Khan, 1962
G (²Σ⁺) 2											G ← X V	46082 (Z)
G (²Σ⁺) 2	↳Khan, 1962
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
D ²Σ^-	(42065)	(1630) 3			[6.296] 4			[3.8E-4]		[1.664]	D → A V	22861.₅ 5
D ²Σ^-	↳Guntsch, 1937; Guntsch, 1939
C ²Π_(r)	(41164) 6	[1623.4] Z			6.161 7	0.144		3.0E-4		1.682	C → A	21956.₅ 5
	↳Pearse, 1929; Guntsch, 1934; Guntsch, 1937, 2; Guntsch, 1939
											C ↔ X V	41235.₉ Z
	↳missing citation; Guntsch, 1935; Grundstrom, 1936; Guntsch, 1937, 2; Turner and Harris, 1937; Guntsch, 1939; missing citation
E ²Σ⁺	(35568)	[1444.8] Z	8		6.23	0.30 9		[3.3E-4] 10		1.67₃	E ← X V_R	35550.6 Z
E ²Σ⁺	↳Khan, 1961; missing citation; Balfour and Cartwright, 1975
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
B' ²Σ⁺	22410.₅	828.₀ Z	11.6 11		[2.596]	12		1.2E-4	0.13E-4	2.597	B' → X R	22081.₉ Z
B' ²Σ⁺	↳Balfour and Cartwright, 1975; Balfour and Cartwright, 1976
A ²Π_r	19226.₈ 13	1598.17 Z	31.08₅ 14	-0.633	6.1913	0.1931 15	0.0005	3.60E-4 16		1.6778	A ↔ X 17 18 V	19278.₄ 5
A ²Π_r	↳Guntsch, 1937; Guntsch, 1939; Balfour, 1970; Balfour, 1970, 2; Balfour and Cartwright, 1976, 2
X ²Σ⁺	0	1495.20 Z	31.889 19	0.384	5.8257	0.1859 20		3.44E-4 16		1.7297 21
X ²Σ⁺	↳Knight and Weltner, 1971

Notes

R shaded band with head at 2100 Å.

V shaded band with head at 2172 Å.

Estimated from w² = 4B³/D and from the observed isotope shift of the 0-0 band.

Spin doubling. |γ| = 0.01.

Average of the two subband origins Guntsch, 1939.

A₀ = (+)3.7; Balfour, 1970, 2 gives -3.7, but his arguments are not conclusive.

The P and R branches of the C→X, 0-0 band break off above N' = 10; bands with v'>0 have Q branches only. The predissociation is caused by B' ²Σ⁺; see Balfour and Cartwright, 1975.

ΔG(3/2)= 1490. The v=2 level was formerly believed to be v=0 of a new ²Σ state (B ²Σ⁺), see Grundstrom, 1936, Grundstrom, 1936, 2, Guntsch, 1938, Guntsch, 1939. Similarly, Khan, 1961 assigned the 1-0 band as 0-0 of a new system F←X.

B₂ = 5.44₈; see 8. Transitions to v=1 are discrete but those to v=2 are diffuse indicating that the state causing the predissociation [B' ²Σ⁺, see Balfour and Cartwright, 1975] crosses the E state potential curve between v=1 and 2. Emissions from v=2 has been observed at high pressure.

D₁ = 4.0E-4; D₂ = 2.7₁E-4; H₂ = +8.₆E-8; (see 8).

The equilibrium constants in Balfour and Cartwright, 1976 do not reproduce the observed intervals, probably owing to an error in ω_ez_e. D_e ~ 10900 cm^-1 Balfour and Cartwright, 1976

B_v(v=1,2,3,4...9) = 2.605, 2.618, 2.608, 2.592, ... 2.419; B_e = 2.585, but the higher order constants of Balfour and Cartwright, 1976 do no reproduce their data. Small perturbations by A ²Π. RKR potential curve Balfour and Cartwright, 1976. See also Sink, Bandrauk, et al., 1976.

A₀= +35.3 Balfour, 1970, 2

These constants (for v≤3) have been recalculated from the three ΔG values obtained by Balfour and Cartwright, 1976, 2; the equilibrium constants determined by Balfour and Cartwright, 1976, 2 do not reproduce their data. D_e ~ 14200 cm^-1 Balfour and Cartwright, 1976, 2.

Small perturbations by B' ²Σ⁺.

D_v increases rapidly with v.

Oscillator strength f₀₀= 0.257 [see Balfour and Cartwright, 1976, 2 and references given there], much larger than the earlier experimental value of Main, Carlson, et al., 1967.

Balfour, 1970 has measured the 0-0 and 0-1 bnads of ²⁵MgH and ²⁶MgH; see also Branch, 1970, Boyer, 1971.

ω_ez_e= -0.113 Balfour and Cartwright, 1976, 2; D_e⁰ ~ 11700 cm^-1 Balfour and Cartwright, 1976, 2.

+0.0039₃(v+1/2)² - 0.0012₃(v+1/2)³. The last term was not reported by Balfour and Cartwright, 1976, 2 but must be included for a satisfactory fit to their data (v=0...6).

ESR sp. 23

From extrapolations of the vibrational levels in X, A and B'. Close agreement with the theoretical value of Meyer and Rosmus, 1975, D₀ = 1.25 eV.

In Ar matrices at 4K.

References

Go To: Top, Constants of diatomic molecules, Notes

Guntsch, 1934
Guntsch, A., Uber das bandenspektrum des magnesiumhydrids, Z. Phys., 1934, 87, 312. [all data]

Guntsch, 1935
Guntsch, A., Uber das ultraviolette bandenspektrum des magnesiumhydrids und magnesiumdeutrids, Z. Phys., 1935, 93, 534. [all data]

Turner and Harris, 1937
Turner, L.A.; Harris, W.T., The ultraviolet bands of magnesium hydride, Phys. Rev., 1937, 52, 626. [all data]

Guntsch, 1939
Guntsch, Dissertation, Stockholm, 1939, 1. [all data]

Khan, 1962
Khan, M.A., MgH bands at 2172, 2100 and 2088 Å and MgD bands at 2172, 2358 and 2364 A, Proc. Phys. Soc. London, 1962, 80, 209. [all data]

Guntsch, 1937
Guntsch, A., Neue untersuchungen uber das bandenspektrum des magnesiumhydrids, Z. Phys., 1937, 104, 584. [all data]

Pearse, 1929
Pearse, R.W.B., The ultra-violet spectrum of magnesium hydride. 1. The band at λ2430, Proc. R. Soc. London A, 1929, 122, 442. [all data]

Guntsch, 1937, 2
Guntsch, A., Uber einige neue banden des magnesiumhydrids, Z. Phys., 1937, 107, 420. [all data]

Grundstrom, 1936
Grundstrom, Dissertation, Stockholm, 1936, 0. [all data]

Khan, 1961
Khan, M.A., MgH and MgD bands at 2819 Å and 2702 Å, Proc. Phys. Soc. London, 1961, 77, 1133. [all data]

Balfour and Cartwright, 1975
Balfour, W.J.; Cartwright, H.M., Low-lying electronic states of magnesium hydride, Chem. Phys. Lett., 1975, 32, 82. [all data]

Balfour and Cartwright, 1976
Balfour, W.J.; Cartwright, H.M., The B'²Σ⁺ → X²Σ⁺ systems of MgH and MgD, Can. J. Phys., 1976, 54, 1898. [all data]

Balfour, 1970
Balfour, W.J., The A²Π → X²Σ⁺ systems of ²⁴MgH, ²⁵MgH, and ²⁶MgH, Astrophys. J., 1970, 162, 1031. [all data]

Balfour, 1970, 2
Balfour, W.J., The electronic spectrum of magnesium hydride and magnesium deuteride, J. Phys. B:, 1970, 3, 1749. [all data]

Balfour and Cartwright, 1976, 2
Balfour, W.J.; Cartwright, H.M., The A²Π-X²Σ⁺ system and dissociation energy of magnesiun hydride, Astron. Astrophys. Suppl. Ser., 1976, 26, 389. [all data]

Knight and Weltner, 1971
Knight, L.B., Jr.; Weltner, W., Jr., Hyperfine interaction and chemical bonding in MgH, CaH, SrH, and BaH molecules, J. Chem. Phys., 1971, 54, 3875. [all data]

Grundstrom, 1936, 2
Grundstrom, B., Absorption spectrum of magnesium hydride in the ultra-violet, Nature (London), 1936, 131, 108. [all data]

Guntsch, 1938
Guntsch, A., Druckeffekt in der magnesiumhydridbande bei λ2590 Å, Z. Phys., 1938, 110, 549. [all data]

Sink, Bandrauk, et al., 1976
Sink, M.L.; Bandrauk, A.D.; Henneker, W.H.; Lefebvre-Brion, H.; Raseev, G., Theoretical study of the low-lying electronic states of MgH, Chem. Phys. Lett., 1976, 39, 505. [all data]

Main, Carlson, et al., 1967
Main, R.P.; Carlson, D.J.; DuPuis, R.A., Measurement of oscillator strengths of the MgO(B¹Σ⁺ - X¹Σ⁺) and MgH(A²Π - X²Σ⁺) band systems, J. Quant. Spectrosc. Radiat. Transfer, 1967, 7, 805. [all data]

Branch, 1970
Branch, D., Isotopes of magnesium in the sun, Astrophys. J., 1970, 159, 39. [all data]

Boyer, 1971
Boyer, R., Isotopic lines of the MgH molecule, Astron. Astrophys., 1971, 12, 464. [all data]

Meyer and Rosmus, 1975
Meyer, W.; Rosmus, P., PNO-Cl and CEPA studies of electron correlation effects. III. Spectroscopic constants and dipole moment functions for the ground states of the first-row and second-row diatomic hydrides, J. Chem. Phys., 1975, 63, 2356. [all data]

Notes

Go To: Top, Constants of diatomic molecules, References

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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