DNP for polarizing liquid DNP for polarizing liquid 33HeHe

Hideaki UematsuHideaki UematsuDepartment of PhysicsDepartment of Physics

For Yamagata UniversityFor Yamagata UniversityPT groupPT group

Yamagata PT group(2006)Yamagata PT group(2006)

Background of the studyBackground of the studyPolarized Polarized 33He targets have been used in He targets have been used in

various scattering experimentsvarious scattering experiments > in > in 33He only neutron is polarizedHe only neutron is polarized > a good target for the study of neutron characteristics > a good target for the study of neutron characteristics > studied only in gas targets> studied only in gas targets

Advantages of polarizing liquid Advantages of polarizing liquid 33HeHe >Density gas:liquid=1:662⇒>Density gas:liquid=1:662⇒ >Its fluidity may allow to make a polarized target with >Its fluidity may allow to make a polarized target with

circulating polarized liquid circulating polarized liquid 33HeHe >Could be applied in many other fields>Could be applied in many other fields

(e.g. medical use, material science, chemistry, etc.)(e.g. medical use, material science, chemistry, etc.) 　　

How to polarize How to polarize 33He in liquid formHe in liquid form1.1. Brute force methodBrute force method

>Polarized liquid is obtained by quickly melting polarized >Polarized liquid is obtained by quickly melting polarized solid solid >55% polarization obtained in solid at 6.6T, 6mK, and >55% polarization obtained in solid at 6.6T, 6mK, and 30bar, G.Bonfait et al. Phys.Rev.Lett. 53(1984)1092 30bar, G.Bonfait et al. Phys.Rev.Lett. 53(1984)1092 >However, it’s difficult to make >However, it’s difficult to make 33He solidHe solid

2.2. Dynamic Nuclear Polarization (DNP)Dynamic Nuclear Polarization (DNP) >>spin-spin coupling between electron and nucleusspin-spin coupling between electron and nucleus >Transferring polarization of electrons to neighboring >Transferring polarization of electrons to neighboring nucleinuclei >able to obtain both positive and negative polarization>able to obtain both positive and negative polarization

US group applied DNP for US group applied DNP for polarizing liquid polarizing liquid 33HeHe

Used powdered sucrose charcoalUsed powdered sucrose charcoalPolarization transfer process:Polarization transfer process:

electron electron → → 11H → H → 33HeHeObtained positive enhancementsObtained positive enhancements

1.18 times1.18 times of TE signal amplitude of TE signal amplitude at at T=1.8KT=1.8K,,B=182GB=182G

Measured relaxation time Measured relaxation time TT11 was was 1.02sec1.02sec L.W.Engel et al 1985L.W.Engel et al 1985

DNP

French group applied DNP for French group applied DNP for polarizing liquid polarizing liquid 33HeHe

Used fluorocarbon beads containing electronic paramagUsed fluorocarbon beads containing electronic paramagnetic centersnetic centers

Polarization transfer process: electron Polarization transfer process: electron → → 1919FF→→33HeHe Obtained enhancements Obtained enhancements

a.a. Positive: Positive: twicetwice of TE signal at of TE signal at T=250mKT=250mK, , B=300GB=300G

b.b. Negative: not mentionedNegative: not mentioned A.Schuhl et al 1985A.Schuhl et al 1985

DNP

3He

19F

H

TE3He

Our New DNP method for polarizing Our New DNP method for polarizing liquid liquid 33HeHe

Direct coupling of a unpaired electron and Direct coupling of a unpaired electron and 33HeHe>using spin-spin interaction of electron and nucleus>using spin-spin interaction of electron and nucleus

Using unpaired electrons in a free radical Using unpaired electrons in a free radical Embedding the free radical into a porous Embedding the free radical into a porous

material material Filling the porous material with liquid Filling the porous material with liquid 33HeHe Irradiating a microwave Irradiating a microwave Free radicalFree radical → → TEMPOTEMPO

Porous materialPorous material → → ZeoliteZeolite

Zeolite and TEMPOZeolite and TEMPO NaY type zeolite (n=51)NaY type zeolite (n=51)

• Super Cage Super Cage Max dia.: 13Max dia.: 13ÅÅ Window dia.: 7.4ÅWindow dia.: 7.4Å

• 4.7x104.7x101919 super cages/g super cages/g• 33He(dia.:3Å) He(dia.:3Å) → → ≈80 ≈80 33He caHe ca

n get in one super cage n get in one super cage TEMPOTEMPO(2,2,6,6-tetramenthyl-piper(2,2,6,6-tetramenthyl-piper

idinyl-1-oxyle)idinyl-1-oxyle)• Melting point: 36 Melting point: 36 ººCC• Boiling point: 67 Boiling point: 67 ººCC• Molecule size: ~7ÅMolecule size: ~7Å

sodalite cage

double T6-ring

Zeolite(NanAlnSi(192-n)O384·240H2O(n=48~76)

HH

CH3

CH3H3CH3C

HH

HH

N

O

TEMPO

7Å

7.4Å

ESR signal of TEMPO in zeoliteESR signal of TEMPO in zeolite

super cage

Embedding TEMPO to ZeoliteEmbedding TEMPO to Zeolite Preparation : Desiccate zeolite Preparation : Desiccate zeolite

at 500 at 500 ººC for 8 hoursC for 8 hours1.1. Dissolve TEMPO in n-pentane Dissolve TEMPO in n-pentane 2.2. Add zeolite to n-pentane solutiAdd zeolite to n-pentane soluti

on on 3.3. Stir n-pentane solution for 8 hoStir n-pentane solution for 8 ho

urs in a sealed vesselurs in a sealed vessel4.4. Evaporate n-pentane in a vacuEvaporate n-pentane in a vacu

um containerum container

500 ºC

Zeolite

Embedding TEMPO to ZeoliteEmbedding TEMPO to Zeolite Preparation : Desiccate zeolite Preparation : Desiccate zeolite

at 500 at 500 ººC for 8 hoursC for 8 hours1.1. Dissolve TEMPO in n-pentane Dissolve TEMPO in n-pentane 2.2. Add zeolite to n-pentane solutioAdd zeolite to n-pentane solutio

n n 3.3. Stir n-pentane solution for 8 hoStir n-pentane solution for 8 ho

urs in a sealed vesselurs in a sealed vessel4.4. Evaporate n-pentane in a vacuEvaporate n-pentane in a vacu

um containerum container

TEMPO

n-pentane

zeolite

Embedding TEMPO to ZeoliteEmbedding TEMPO to Zeolite Preparation : Desiccate zeolite Preparation : Desiccate zeolite

at 500 at 500 ººC for 8 hoursC for 8 hours1.1. Dissolve TEMPO in n-pentane Dissolve TEMPO in n-pentane 2.2. Add zeolite to n-pentane solutiAdd zeolite to n-pentane soluti

on on 3.3. Stir n-pentane solution for 8 hoStir n-pentane solution for 8 ho

urs in a sealed vesselurs in a sealed vessel4.4. Evaporate n-pentane in a vacuEvaporate n-pentane in a vacu

um containerum container

Embedding TEMPO to ZeoliteEmbedding TEMPO to Zeolite Preparation : Desiccate zeolite Preparation : Desiccate zeolite

at 500 at 500 ººC for 8 hoursC for 8 hours1.1. Dissolve TEMPO in n-pentane Dissolve TEMPO in n-pentane 2.2. Add zeolite to n-pentane solutiAdd zeolite to n-pentane soluti

on on 3.3. Stir n-pentane solution for 8 hoStir n-pentane solution for 8 ho

urs in a sealed vesselurs in a sealed vessel4.4. Evaporate n-pentane in a vacuEvaporate n-pentane in a vacu

um containerum container

R

Experimental setupExperimental setup Experimental cell Experimental cell

made of a PET tube made of a PET tube and a VCR gas and a VCR gas connector connector

Volume : 2.5ccVolume : 2.5cc Experimental cell Experimental cell

filled with zeolite filled with zeolite tightly and quickly tightly and quickly

Experimental cellImage of experimental chamber

Thermal equilibrium signal of Thermal equilibrium signal of 33HeHe

TE signal of liquid TE signal of liquid 33HeHeT=1.42KT=1.42K , ,B 2.5T≒B 2.5T≒

ee-- spin density : spin density :1.3×101.3×101919spins/ccspins/cc T=1.47KT=1.47K, , B 2.5T≒B 2.5T≒

Low concentration of TEMPOLow concentration of TEMPO

ee-- spin density : spin density :4.5×104.5×101818spins/ccspins/cc T=1.54KT=1.54K, , B 2.5T≒B 2.5T≒

High concentration of TEMPOHigh concentration of TEMPOBulk Bulk 33He (without zeolite)He (without zeolite)

Symmetric signal when in zeoiteSymmetric signal when in zeoite

Narrower width for low spin densityNarrower width for low spin density

Bulk Bulk 33He signal shows asymmetric shapeHe signal shows asymmetric shape

TE signals fitted with Lorentzian TE signals fitted with Lorentzian

TE signal of liquid TE signal of liquid 33HeHeT=1.42KT=1.42K , ,B 2.5T≒B 2.5T≒

spin density :spin density :1.3×101.3×101919spins/ccspins/cc T=1.47KT=1.47K, , B 2.5T≒B 2.5T≒

spin density :spin density :4.5×104.5×101818spins/ccspins/cc T=1.54KT=1.54K, , B 2.5T≒B 2.5T≒

Low concentrationLow concentrationHigh concentrationHigh concentration

Extent: 44.4ppmExtent: 44.4ppm

Bulk 3He(without zeolite)Bulk 3He(without zeolite) Red line shows the Red line shows the LorentzianLorentzian

Center frequency of Center frequency of 33He: He: 81.09MHz (in 2.5T)81.09MHz (in 2.5T)

Extent: 202ppmExtent: 202ppm Extent: 202ppmExtent: 202ppm

Relaxation time of liquid Relaxation time of liquid 33HeHe

Fitting functionFitting function

dTbtatS

1

exp

S: area of the NMR signalS: area of the NMR signal

time development of NMR signal of liquid time development of NMR signal of liquid 33He inside zeoliteHe inside zeoliteT=1.44KT=1.44K,, B=2.5T B=2.5T, spin density: , spin density: 1.3×101.3×101919 spin/cc spin/cc

Spin relaxation time:Spin relaxation time:TT11=330sec=330sec

3He in zeolite with TEMPO

Positive enhancement by DNPPositive enhancement by DNP

↑↑TE signal TE signal T=1.48KT=1.48K, , B 2.5T≒B 2.5T≒

↑↑max polarized signalmax polarized signal B 2.5T≒B 2.5T≒

observed positive enhancement observed positive enhancement S/SS/STETE =2.34 =2.34

spin density=spin density=4.5×104.5×101818 (low concentration)(low concentration)

Negative enhancement by DNPNegative enhancement by DNP

↑↑TE signalTE signal T=1.53KT=1.53K,, B 2.5T≒ B 2.5T≒

↑↑max polarized signalmax polarized signal B 2.5T≒B 2.5T≒

observed negative enhancementobserved negative enhancementS/SS/STETE =-1.59 =-1.59

spin density=spin density=4.5×104.5×101818

Micro wave frequency dependence Micro wave frequency dependence

fc: ESR center frequencyfc: ESR center frequency of TEMPO(=70.22GHz)of TEMPO(=70.22GHz)

spin density:spin density:1.3×101.3×101919, , B 2.5T≒B 2.5T≒

at 2.5T expected ESR line at 2.5T expected ESR line width for TEMPO is 340MHzwidth for TEMPO is 340MHz

Observed line width wasObserved line width wasnarrower than expectednarrower than expected

SummarySummary We obtained the thermal equilibrium signal of We obtained the thermal equilibrium signal of

liquid liquid 33He in zeolite.He in zeolite. A narrow signal was observed with low concA narrow signal was observed with low conc

entration of TEMPO.entration of TEMPO. We measured relaxation time of We measured relaxation time of 33He in zeolitHe in zeolit

e (It is a few minutes at 2.5T)e (It is a few minutes at 2.5T) We obtained polarization enhancements for liWe obtained polarization enhancements for li

quid quid 33He in zeolite by DNP.He in zeolite by DNP. The enhancements were larger than ever before The enhancements were larger than ever before

(obtained by DNP).(obtained by DNP). They may be improved by tuning the conditions.They may be improved by tuning the conditions.

Thank you for listeningThank you for listening

Zeolite and its characterZeolite and its character Mineral which has a micro-porous structure, high Mineral which has a micro-porous structure, high

hydrophobicity, thermostability and mostly used hydrophobicity, thermostability and mostly used as a catalyst, ion exchanger, absorber as a catalyst, ion exchanger, absorber

(Na(NannAlAlnnSiSi(192-n)(192-n)OO384384·240H·240H22OO(n=48~76(n=48~76)) Used (HSZ-300serise)TOSOH corporationUsed (HSZ-300serise)TOSOH corporation

Cation type: NaCation type: Na SiOSiO22/Al/Al22OO33(mol/mol): 5.5(mol/mol): 5.5 Na2O(wt%): 12.5Na2O(wt%): 12.5 U.C.C. by ASTM :24.63U.C.C. by ASTM :24.63 NH3-TPD(mmol/g): -NH3-TPD(mmol/g): - Surface Area(BET, m2/g): 700Surface Area(BET, m2/g): 700 Crystal Size(Crystal Size(μμmm): 0.3): 0.3 Mean Particle Size(μm): 6Mean Particle Size(μm): 6

Decrease of TEMPO in ZeoliteDecrease of TEMPO in Zeolite

Spin density :7.5Spin density :7.5×10×101818spin/ccspin/ccRoom temperature Room temperature

n-pentane n-pentane CC55HH1212

melting point: -131melting point: -131ºCºC boiling point: 36.07ºCboiling point: 36.07ºC

123

3

127

1038.1

13.2

1005.5

KJk

TJkTBP

B

NHe

TE

N

→0.13% ccspin /105.4 18

Density of liquid Density of liquid 33HeHe in 1g zeolitein 1g zeolite

23.1mg 23.1mg