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

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

Brief review on NMR   * *cited from: https://en.wikipedia.org/wiki/Relaxation_%28NMR%29

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

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

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

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

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

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?

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:10.3969/j.issn.0509-4038.2005.10.014.

Effects of ions Alkaline ions have LITTLE magnetic moment(~ 1 1000 𝜇 𝐶𝑢 ) Adding 𝐾𝐶𝑙 to 50% ethanol-water mixture A decrease of ~8% in 𝑇 2

Effects of ions An approximate linear relation was observed too

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

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

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

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

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

References Wikipedia: relaxation(NMR), https://en.wikipedia.org/wiki/Relaxation_%28NMR%29 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:10.3969/j.issn.0509- 4038.2005.10.014.