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Barium (Ba) has two low sensitivity NMR active nuclei, ¹³⁵Ba and ¹³⁷Ba. ¹³⁷Ba is more sensitive but yields broader signals than ¹³⁵Ba (fig. 1). ¹³⁷Ba is the preferred barium nucleus as resolution has yet to be shown to be important because no barium NMR spectrum containing more than one peak has been reported. Both nuclei are quadrupolar and yield very broad signals even in symmetric environments. Barium has a narrow chemical shift range, narrower than its line-width. As a result barium NMR is hardly used and when used, it is for determining its aqueous binding properties from its relaxation rate.

Fig. 1. Comparison of ¹³⁵Ba and ¹³⁷Ba NMR for BaCl₂ (1 M) in D₂O

There is hardly any information about barium chemical shifts (fig. 2).

Fig. 2. Chemical shift ranges for barium NMR

¹³⁵Barium NMR

¹³⁵Ba (fig. 3) yields signals that are less sensitive and broad than ¹³⁷Ba. However, because no spectrum showing more than one barium signal has been reported, resolution is not important so ¹³⁷Ba NMR is the preferred barium nucleus.

Fig. 3. ¹³⁵Ba NMR for BaCl₂ (1 M) in D₂O

Properties of ¹³⁵Ba

(Click here for explanation)

Property	Value
Spin	3/2
Natural abundance	6.592%
Chemical shift range	20 ppm, from -15 to 5
Frequency ratio (Ξ)	9.934457%
Reference compound	0.5 M BaCl2 in D2O
Linewidth of reference	707 Hz
T1 of reference	0.00022 s
Receptivity rel. to 1H at natural abundance	3.30 × 10-4
Receptivity rel. to 1H when enriched	5.01 × 10-3
Receptivity rel. to 13C at natural abundance	1.93
Receptivity rel. to 13C when enriched	29.3
Linewidth parameter	340 fm4

¹³⁷Barium NMR

¹³⁷Ba (fig. 4) yields signals that are more sensitive and broader than ¹³⁵Ba. However, because no spectrum showing more than one barium signal has been reported, resolution is not important so ¹³⁷Ba NMR is the preferred barium nucleus.

Fig. 4. ¹³⁷Ba NMR for BaCl₂ (1 M) in D₂O

Properties of ¹³⁷Ba

(Click here for explanation)

Property	Value
Spin	3/2
Natural abundance	11.232%
Chemical shift range	20 ppm, from -15 to 5
Frequency ratio (Ξ)	11.112928%
Reference compound	0.5 M BaCl2 in D2O
Linewidth of reference	1425 Hz
T1 of reference	0.00006 s
Receptivity rel. to 1H at natural abundance	7.87 × 10-4
Receptivity rel. to 1H when enriched	7.01 × 10-3
Receptivity rel. to 13C at natural abundance	4.62
Receptivity rel. to 13C when enriched	41.1
Linewidth parameter	800 fm4

Safety note

Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, soluble barium salts including BaCl₂ are toxic (LD₅₀ 1 g) insoluble salts are less toxic: wear gloves.

References

• O. Lutz and H. Oehler, "Barium-135 and -137 Fourier transform NMR and NQR studies", Z. Phys. A, 288, 11-15 (1978).
• H. Krueger, O. Lutz and H. Oehler, H. "Nuclear magnetic moments and ratios of quadrupole moments barium-135 and -137 and lanthanum-138 and -139 by NMR spectroscopy", Phys. Lett. A, 62A, 131-2 (1977).
• V. I. Chizhik, "NMR relaxation and microstructure of aqueous electrolyte solutions", Mol. Phys., 90, 653-659 (1997).