1. NMR EXPERIMENT ON TRANSVERSE RELAXATION TIME
——based on ethanol-water mixture
Reporters: Tong Chen, Ying Xu
Instructor: Xi Yu

2. Outline Brief review on NMR: resonance, FID, echo-wave
System with little impurity: viscosity and relaxation
Effects of ions: paramagnetic, alkaline
Conclusions & remarks

3. Brief review on NMR *
*cited from:

4. BPP theory Spin-lattice interaction Brownian motion Magnetic dipole
Spin rotation
randomly

5. BPP theory In gas or liquid, 𝑇 1 ≈ 𝑇 2
𝜏 𝑐 represent the characteristic time of Brownian motion
𝜂: viscosity; 𝑁 0 : number density; 𝑇: temperature
Debye’s relation was used to replace 𝜏 𝑐 which states 𝜏=4𝜋 𝑎 3 𝜂/𝑘𝑇 where 𝑎 is the radius of a molecule

6. System with little impurity
Experiment set up:
Apparatus: mesoMR23-060H-I
Under 32.00±0.01℃, 0.5±0.05𝑇
𝑇 2 of 1 𝐻 was measured for different ethanol-water volume ratio with the total volume fixed at 20ml

7. System with little impurity
Transverse relaxation time 𝑇 2 vs volume fraction
Pure water: 2518ms
Pure ethanol: 1840ms
Minimum: 1410ms
~70%

8. System with little impurity
Comparison with the viscosity-mass fraction 1/𝜂−𝑊 relation
~64%
~40%

9. System with little impurity
Similar features are observed in both curves
1/𝑇 2 is not exactly proportional to 𝜂
1 𝑇 2 𝜂 =𝐴 𝑎 3 +𝐵 𝑁 0 const
𝑁 0 ∝ 𝑉 𝑎 3
in pure water, 𝐴 𝑎 3 ~𝐵 𝑁 0 , thus a maximum is comprehensible if 𝑎 changes
CONSTANT?

10. Effects of ions Paramagnetic ions: fixed 𝜇 𝑒𝑓𝑓
( 1 𝑇 1 ) 𝑛 ∝ 𝜇 𝑒𝑓𝑓 2 𝑁 0 𝜂/𝑇∝ 𝑁 0 *
A decrease of >90% in 𝑇 2
*cited from: 臧充之,张洁天,彭培芝等.核磁共振弛豫时间与溶液浓度关系的实验研究[J].物理通报,2005,(10):30-32.DOI: /j.issn

11. Effects of ions
Alkaline ions have LITTLE magnetic moment(~ 𝜇 𝐶𝑢 )
Adding 𝐾𝐶𝑙 to 50% ethanol-water mixture
A decrease of ~8% in 𝑇 2

12. Effects of ions
An approximate linear relation was observed too

13. Effects of ions
Experiment set up:
𝑇 2 of 1 𝐻 was measured for different ethanol-water volume ratio, while the concentration(mole per volume of water) of 𝑁𝑎𝐶𝑙 varies

14. Effects of ions 0%
ethanol
20%
ethanol
40%
ethanol
50%
ethanol

15. Effects of ions
𝑁𝑎𝐶𝑙,𝐾𝐶𝑙 are slightly soluble in ethanol
𝑁𝑎𝐶𝑙,𝐾𝐶𝑙 crystals are paramagnetic
Some 𝑁𝑎𝐶𝑙 may not ionized, and can provide the magnetic moment needed for the interaction

16. Conclusions & Remarks
The effects of spin-lattice interaction can be partially described by the macroscopic parameter 𝜂 in liquid with little impurity
The effects of ions on relaxation time are mainly due to paramagnetism

17. Conclusions & Remarks Lack of direct evidences of unionized 𝑁𝑎𝐶𝑙,𝐾𝐶𝑙
Data are limited by the solubility of 𝑁𝑎𝐶𝑙,𝐾𝐶𝑙

18. References Wikipedia: relaxation(NMR),
Bloembergen N, Purcell E M, Pound R V. Relaxation effects in nuclear magnetic resonance absorption[J]. Physical Review, 1948, 73(7): 679.
臧充之,张洁天,彭培芝等.核磁共振弛豫时间与溶液浓度关系的实验 研究[J].物理通报,2005,(10):30-32.DOI: /j.issn