STUDIES OF SURFACE PROPERTIES OF ICE USING NUCLEAR MAGNETIC RESONANCE

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STUDIES OF SURFACE PROPERTIES OF ICE USING NUCLEAR MAGNETIC RESONANCE

Y. Mizuno, N. Hanafusa

To cite this version:

Y. Mizuno, N. Hanafusa. STUDIES OF SURFACE PROPERTIES OF ICE USING NUCLEAR MAGNETIC RESONANCE. Journal de Physique Colloques, 1987, 48 (C1), pp.C1-511-C1-517.

�10.1051/jphyscol:1987170�. �jpa-00226316�

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JOURNAL DE

PHYSIQUE

C o l l o q u e

C 1 ,

supplgment a u n o 3, Tome 48, mars

1987

STUDIES OF SURFACE PROPERTIES OF ICE USING NUCLEAR MAGNETIC RESONANCE

Y. M I Z U N O

and

N.

HANAFUSA

I n s t i t u t e o f Low Temperature S c i e n c e s , HoWraido U n i v e r s i t y , Sapporo 060, J a p a n

R 6 s d - Des e e r i e n c e s de rdsonance magndtique nucldaixe pul&e ont dt6 f a i t e s sur des p e t i t e s particules de glace ayant un grand rapport surface/volume pour dtudier l a couche quasi liquide

(Q.L.L.)

2 l a surface de l a glace. La &pendance avec l a t d r a t u r e des caract6ristiques

IWN

e t l e s propridtds dynamiques t e l l e s que l e temps de c o r r d l a t i o n pour l e mouvement de r o t a t i o n e t l e c o e f f i c i e n t d ' a u t o - d i f f u s i o n de l a Q.L.L. o n t 6 t d d d c r i t e s . La frdquence du mouvement moldcaaire rotationnel dans l e

Q.L.L.

e t l e coefficient d'autc-diffusion sont plus grands respectivement de 5 et

2

ordres de grandeur que dans l a glace en volume.

Abstract - Pulsed nuclear mgnetic resonance studies were carried out on small i c e p a r t i c l e s

with

large surface to volume r a t i o s to investigate the so-called quasi- liquid layer

(Q.L.L.)

on an i c e surface. The temperature dependence of features of

the N M R spectra and dynamical properties such as

the correlation

time

f o r rota- tional m t i o n and the self diffusion coefficient of the

Q.L.L.

were described. The frequency of the rotational mlecular m t i o n

and

the self diffusion coefficient were larger than those of bulk i c e

by

about five orders and by two orders, respec-

tively.

I .

I n t r o d u c t i o n

I t

i s g e n e r a l l y a c c e p t e d t h a t a mobile p h a s e , t h e s o - c a l l e d q u a s i - l i q u i d l a y e r

( Q . L . L . )

on an i c e s u r f a c e , p l a y s an i m p o r t a n t r o l e i n some phenomena which o c c u r a t t e m p e r a t u r e s n e a r below t h e m e l t i n g p o i n t , s u c h a s snow metamorphism, s i n t e r i n g , a d h e s i o n , a c c r e t i o n and c r y s t a l growth. Many s t u d i e s r e l a t e d t o t h e

Q . L . L .

have been c a r r i e d o u t i n t h e p a s t

30

y e a r s t o c l a r i f y i t s e x i s t e n c e and t h e d i s t i n c t i v e s u r f a c e p r o p e r t i e s o f i c e .

Nakaya

( 1 )

and Weyl

( 2 )

have i n t e r p r e t e d t h e a d h e s i o n o b s e r v e d be- tween i c e s p h e r e s and r e g e l a t i o n i n t e r m s o f mobile I l l i q u i d - l i k e " s u r - f a c e s t r u c t u r e s . J e l l i n e k

( 3 )

emphasized t h e e x i s t e n c e of t h e mobile phase b a s e d on e x t e n s i v e s t u d i e s on i c e a d h e s i o n and reviewed t h e s u r - f a c e p r o p e r t i e s o f i c e .

On t h e o t h e r h a n d , F l e t c h e r

( 4 )

h a s shown t h e o r e t i c a l l y t h e e x i s - t e n c e o f t h e p r o p e r s u r f a c e s t r u c t u r e and concluded t h a t a t tempera- t u r e s above a b o u t - 5 ' ~ th e s u r f a c e of i c e i s covered by t h e Q.L.L., whose t h i c k n e s s i n c r e a s e s a s t h e t e m p e r a t u r e a p p r o a c h e s O°C.

D i r e c t e v i d e n c e o f t h e e x i s t e n c e of t h e

Q . L . L .

on i c e s u r f a c e s h a s been p r e s e n t e d by many i n v e s t i g a t o r s u s i n g v a r i o u s e x p e r i m e n t a l t e c h - n i q u e s : Photoemission by Nason and F l e t c h e r ( 5 1 , p r o t o n c h a n n e l l i n g by Golecki and J a c c a r d

( 6 )

and n u c l e a r magnetic r e s o n a n c e by K v l i v i d z e e t a l .

( 7 1 ,

Anderson

( 8 ) ,

B e l l e t a 1 . ( 9 ) and Ocampo and K l i n g e r ( 1 0 ) .

A

r e c e n t e l l i p s o m e t r i c a l s t u d y by Furukawa e t a l . ( l l ) p r o v i d e d de- t a i l e d i n f o r m a t i o n on t h e t h i c k n e s s and r e f r a c t i v e i n d e x of t h e l a y e r and i t s dependence on t h e c r y s t a l l o g r a p h i c s u r f a c e . T h e i r r e s u l t s on t h e c r y s t a l l o g r a p h i c s u r f a c e s u p p o r t t h e t h e o r e t i c a l t r e a t m e n t of t h e

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987170

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C1-512 JOURNAL

DE

PHYSIQUE

growth k i n e t i c s o f i c e from t h e vapor phase p r e s e n t e d by Kuroda and Lacmann

(

12

)

.

I n f o r m a t i o n on t h e dynamical p r o p e r t i e s o f t h e

Q . L . L . ,

i t s d i f f e r - e r e n c e from b u l k i c e o r i t s " l i q u i d - l i k e v f e a t u r e , i s i m p o r t a n t t o un- d e r s t a n d t h e above-mentioned snow and i c e phenomena which a r e c l o s e l y r e l a t e d t o t h e s u r f a c e p r o p e r t i e s o f i c e .

. I n t h i s c o n n e c t i o n , t h i s p a p e r d e s c r i b e s t h e dynamical p r o p e r t i e s o f t h e Q.L.L., t h e c o r r e l a t i o n time f o r r o t a t i o n a l m o l e c u l a r motion and t h e s e l f d i f f u s i o n c o e f f i c i e n t i n t h e Q.L.L. u s i n g p u l s e d n u c l e a r mag- ne t i c resonance.

11.

Experimental P r o c e d u r e s

I n o r d e r t o o b t a i n t h e NMR s i g n a l due t o i c e s u r f a c e s , s m a l l i c e p a r t i c l e s o f l e s s t h a n 150 pm i n d i a m e t e r were p r e p a r e d a t -30°C by f r e e z i n g s u p e r c o o l e d w a t e r d r o p l e t s s p r a y e d o u t from a n a t o m i z e r on a c l e a n t e f l o n s h e e t . The p a r t i c l e s were p u t i n t o a g l a s s c e l l f o r t h e

NMR

s p e c t r o s c o p y . To p r e v e n t s i n t e r i n g between i c e p a r t i c l e s , t h e g l a s s c e l l was s t o r e d i n a c o l d chamber whose t e m p e r a t u r e was k e p t below -80°C.

T h e NMR measurements were made u s i n g a JEOL F X l O O N M R

s p e c t r o s c o p e eqyipped w i t h a s p i n l o c k i n g u n i t and a t e m p e r a t u r e c o n t r o l l i n g u n i t and o p e r a t e d a t 100

MHz.

The t e m p e r a t u r e o f a sample was c o n t r o l l e d w i t h an accuracy o f * O.l°C, and f o r t h e r m a l e q u i l i b r i u m , e v e r y mea- surement performed a t a c e r t a i n t e m p e r a t u r e w a s s t a r t e d a f t e r k e e p i n g t h e sample f o r more t h a n

30

m i n u t e s a t t h a t t e m p e r a t u r e .

To o b t a i n t h e t e m p e r a t u r e dependence on b o t h t h e i n t e n s i t y and t h e l i n e w i d t h , most of t h e measurements were made i n t h e p r o c e s s o f t h e t e m p e r a t u r e r i s i n g from

- 1 0 O 0 C

t o -5°C.

S p i n l a t t i c e r e l a x a t i o n t i m e T I and t h a t i n a r o t a t i n g frame

T I P

were measured by t h e i n v e r s i o n r e c o v e r y and t h e s p i n l o c k i n g methods, r e s p e c t i v e l y .

111.

R e s u l t s

1. NMR

s i g n a l due t o s u r f a c e mobile phase F i g u r e

1

shows

NMR

s p e c t r a f o r t h e s u r f a c e mobile phase accumulated 200 t i m e s a t t h e v a r i o u s tem- p e r a t u r e s observed a t

9 9 . 5 MHz,

t h e b r o a d s i g n a l due t o c r y s t a l l i n e i c e i s n o t s e e n w i t h i n t h e range o f o b s e r v a t i o n a l f r e q u e n c y o f 20 kHz.

The narrow s i g n a l was n o t d e t e c t e d a t any t e m p e r a t u r e when o n l y b u l k i c e was u s e d , and t h e s i g n a l s a p p e a r i n g i n F i g .

1

were t h o u g h t t o be caused by a mobile phase a t an i n t e r f a c e between a i r and c r y s t a l - l i n e i c e a n d / o r a t g r a i n b o u n d a r i e s .

A s i s

obvious i n t h e f i g u r e , t h e l i n e width and t h e i n t e n s i t y v a r y w i t h t e m p e r a t u r e .

I t

s h o u l d be n o t e d t h a t t h e l i n e w i d t h o f t h e spec-

trum a t -lO°C is a b o u t

7

t i m e s t h a t o f o r d i n a r y w a t e r a t +5OC, which i s shown f o r comparison on t h e l e f t hand s i d e . The i n t e n s i t y o f t h e spectrum i s p r o p o r t i o n a l t o t h e number of t h e mobile molecules. The r e l a t i v e i n t e n s i t y , which i s normalized w i t h t h e i n t e n s i t y a t -5"C, and t h e l i n e width v a r i a t i o n w i t h t e m p e r a t u r e a r e shown i n Fig. 2 .

A s

t h e s u r f a c e a r e a was reduced by s i n t e r i n g i n o u r e x p e r i m e n t , t h e i n t e n s i t y , e s p e c i a l l y a t -5OC, i s e x p e c t e d t o be l a r g e r . Although t h e r e l a t i v e i n t e n s i t y l a r g e l y changed between -5OC and -lO°C, l i n e w i d t h v a r i a t i o n was q u i t e s m a l l .

2.

S p i n - l a t t i c e r e l a x a t i o n t i m e ( T 1 ) The s p i n l a t t i c e r e l a x a t i o n t i m e ,

TI, was measured by t h e i n v e r s i o n r e c o v e r y method a t v a r i o u s tempera-

t u r e s . F i g u r e 3 shows t h e r e l a t i o n s between TI and t h e t e m p e r a t u r e

f o r powder i c e p a r t i c l e s and a r e f r o z e n i c e , where e a c h p o i n t i s an av-

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e r a g e o f t h r e e t i m e s measurements i n b o t h c a s e s . The r e f r o z e n i c e was made by m e l t i n g t h e powder i c e s l i g h t l y w i t h i n t h e c e l l and t h e r e a f t e r f r e e z i n g

i t

r a p i d l y a t below - 3 0 ' ~ . M i c r o s c o p i c a l o b s e r v a t i o n r e v e a l - e d t h a t a l a r g e number o f t i n y b u b b l e s s e v e r a l 10 pm i n d i a m e t e r were d i s p e r s e d u n i f o r m l y i n t h e sample.

Figure 1. NMR spectra of the Q.L.L. observed a t 99.5 MHz. Signal of liquid water was taken a t ^+5OC.Notice the dif- ference in the line w i d t h between liquid water and the Q.L.L.

Figure 2. Intensity(so1id l i n e ) and line w i d t h variation(dotted l i n e ) w i t h temperature

The v a r i a n c e i n TI between t h e two samples r e f l e c t s some o f t h e dynamical d i f f e r e n c e s e x p e c t e d t o be c a u s e d mainly by w a t e r vapor p r e s - s u r e around t h e i n n e r and t h e o u t e r s u r f a c e s . However, T I minimum a p p e a r e d around -35OC i n b o t h samples.

The s p i n l a t t i c e r e l a x a t i o n time T I f o r p r o t o n

i s

e x p r e s s e d i n t h e f o l l o w i n g form ( 1 3 ) ,

where,

w, = F

Ho

i s

t h e r e s o n a n t f r e q u e n c y , 7f

i s

t h e gyromagnetic r a t i o ,

r i s

t h e s p i n t o s p i n d i s t a n c e and Z

i s

t h e c o r r e l a t i o n time f o r r o t a - t i o n a l m o l e c u l a r motion. The c o r r e l a t i o n t i m e a t - 3 5 O ~ was e v a l u a t e d t o be 9 . 6 x 1 0 - ~ ~ s e c from t h e c o n d i t i o n t h a t T i

i s

minimum f o r woZ i s a b o u t 0.6. Using t h i s c o r r e l a t i o n t i m e , t h e s p i n t o s p i n d i s t a n c e , r , was e v a l u a t e d t o be a b o u t 1 . 6 6 ~ 1 0 - l o

m

and 1 . 4 1 ~ 1 0 - ~ ~

m

f o r powder and r e f r o z e n i c e , r e s p e c t i v e l y . Assuming

r

d o e s n o t change w i t h tempera- t u r e , ~ a t e a c h t e m p e r a t u r e c a n be o b t a i n e d by s u b s t i t u t i n g t h e c o r r e - sponding T1 i n t o e q . ( 1 ) . I n t h i s c a s e , woz<< 1 i s r e a s o n a b l y c o n s i d - e r e d a t h i g h e r t e m p e r a t u r e s and

wof;)

1

a t

lower t e m p e r a t u r e s compared t o t h e minimum p o i n t g i v e n i n F i g . 3.

F i g u r e 4 i l l u s t r a t e s t h e c o r r e l a t i o n t i m e a t v a r i o u s t e m p e r a t u r e s , where t h e v a l u e a t O°C was c a l c u l a t e d by u s i n g T i a t

o0C,

which was o b t a i n e d by e x t r a p o l a t i n g s e v e r a l p o i n t s a t lower t e m p e r a t u r e s .

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JOURNAL

DE

PHYSIQUE

a: powder ice(o) b: refrozen ice(.)

C 0

0 activation energy

a: 28.0 k~.mol.'

Figure 3 . Spin l a t t i c e relaxation time, Figure 4. Correlation time for rotation-

T I , VS. inverse temperature a l motion, Z

,

vs. inverse temperature

The d i f f e r e n c e i n T f o r powder and r e f r o z e n i c e i s c o n s i d e r a b l y l a r g e n e a r t h e m e l t i n g p o i n t ; however,

i t

d e c r e a s e s a s t e m p e r a t u r e f a l l e s , and below -15OC, b o t h samples become a l m o s t e q u a l . The a c t i - v a t i o n energy f o r r o t a t i o n a l motion was 28.0 kJ/mol f o r powder i c e and 59.7 kJ/mol f o r r e f r o z e n i c e i n t h e t e m p e r a t u r e range o f 0 t o -50°C and 0 t o -15OC, r e s p e c t i v e l y .

A s

i s

shown i n F i g . 4 , t h e c o r r e l a t i o n time o f t h e Q . L . L . i s i n t h e o r d e r o f 1 0 -I0 s e c , which i s much c l o s e r t o t h a t o f w a t e r o f 10-l2 s e c

( 1 4 ) t h a n t h a t o f i c e c r y s t a l o f s e c ( l 5 ) . A s compared w i t h t h e c o r r e l a t i o n time of t h e Q . L . L . a t O°C and t h a t o f o r d i n a r y w a t e r , t h e Q.L.L. i s movable w i t h a f r e q u e n c y o f about 1 / 2 5 o f t h a t i n o r d i - n a r y w a t e r a t O°C.

3. D i f f u s i o n c o e f f i c i e n t For p r o t o n , whose n u c l e u s p o s s e s s e s s p i n 1 / 2 , t h e s p i n l a t t i c e r e l a x a t i o n time i n a r o t a t i n g f r a m e , T l p

,

i s r e l a t e d t o w l , t h e r a d i o f r e q u e n c y , and D , t h e s e l f d i f f u s i o n c o e f f i - c i e n t , a s f o l l o w s ( 1 6 ) :

where N

i s

t h e number d e n s i t y o f r e s o n a n t n u c l e i . A s i s o b v i o u s i n e q . ( 2 1 ,

i n

p l o t t i n g l / T l p v s . ~ $ 1 2 , t h e s l o p e g i v e s a s e l f d i f f u s i o n c o e f f i c i e n t , D. A t y p i c a l r e s u l t a t -lO°C i s shown i n F i g . 5. We o b t a i n e d t h e s e l f d i f f u s i o n c o e f f i c i e n t a t t e m p e r a t u r e s between -1.5"C a n d - 2 0 ° C . T h e r e s u l t s a r e l i s t e d i n T a b l e 1 , w h e r e e v e r y v a l u e i s a n a v e r a g e of t h r e e measurements a t e a c h t e m p e r a t u r e .

A c t i v a t i o n e n e r g y f o r d i f f u s i o n by t r a n s l a t i o n a l motion was e v a l u - a t e d t o be 2 3 . 5 kJ/mol a s i s shown i n F i g . 6 . F o r comparison, t h e d i f - f u s i o n c o e f f i c i e n t i n a s i n g l e c r y s t a l by I t a g a k i ( l 7 ) , i n p o l y c r y s t a l - l i n e i c e by Kuhn and T h i i r k a u f ( l 8 ) and i n w a t e r ( l 4 ) a r e a l s o shown i n t h e same f i g u r e .

The a b s o l u t e v a l u e of t h e d i f f u s i o n c o e f f i c i e n t o f t h e Q . L . L .

i s

a b o u t f o u r o r d e r s of magnitude s m a l l e r t h a n t h a t o f w a t e r ; however,

i t

i s r e m a r k a b l e t h a t t h i s v a l u e i s l a r g e r t h a n t h a t o f a s i n g l e c r y s t a l o f i c e by two o r d e r s . I n r e g a r d t o t h e a c t i v a t i o n e n e r g y f o r d i f f u s i o n , t h a t

(6)

of t h e

Q.L.L. i s

s l i g h t l y l a r g e r t h a n t h a t o f l i q u i d w a t e r b u t i s o n l y a b o u t a t h i r d of a s i n g l e c r y s t a l of i c e .

Table 1

Temperature D i f f u s i o n c o e f f i c i e n t

Figure 5. Tlpvariation with radio fre- quency at

-lO°C;

plotted

1/Tlp

vs. w:/*

*rat*, (5-2O.C) D - Z ~ ~ O - * rnlsec"

18.9 rJ. moi'

'.,

single crystd(ref.17)

'. '.,

^63.1( 0 6 5 e V ) ^kI.mol1

Figure 6. Diffusion coefficient of the Q.L.L. vs. inverse temperature

I V .

D i s c u s s i o n and Conclusion

The i n t e n s i t y o f t h e

NMR s i g n a l was l a r g e l y dependent on t h e p a r t i -

c l e s i z e .

I n

f a c t , i n o u r experiment u s i n g i c e p a r t i c l e s l a r g e r t h a n 200 pm i n d i a m e t e r , t h e s i n g n a l was s m a l l and f a i n t even a t -lO°C.

However, t h e s i z e o f an i n d i v i d u a l c r y s t a l i n an i c e p a r t i c l e was most- l y independent of t h e p a r t i c l e s between 50 and 500 pm i n d i a m e t e r . T h e r e f o r e t h e

NMR

s i g n a l

i s

c o n s i d e r e d t o be due mainly t o i n n e r o r o u t e r f r e e s u r f a c e s and t h e c o n t r i b u t i o n from g r a i n . b o u n d a r i e s seems t o be s m a l l i n t h i s c a s e . Undoubtedly, t h e e x i s t e n c e o f t h e mobile w a t e r phase a t g r a i n b o u n d a r i e s a t v e r y c l o s e t o t h e m e l t i n g p o i n t h a s been shown by Ohtomo and Wakahama(l9). F u r t h e r s t u d i e s a r e needed t o c l a r - i f y t h e d i f f e r e n c e between t h e dynamical p r o p e r t i e s o f a f r e e s u r f a c e and of a g r a i n boundary, because molecules a t t h e g r a i n boundary a r e e x p e c t e d t o have a h i g h e r c r y s t a l l i n i t y t h a n t h o s e i n a f r e e s u r f a c e .

A s

t h e s u r f a c e a r e a d e c r e a s e s due t o s i n t e r i n g between i c e p a r -

t i c l e s , t h e i n t e n s i t y v a r i a t i o n w i t h t e m p e r a t u r e does n o t c o r r e s p o n d t o

t h e t h i c k n e s s v a r i a t i o n o f t h e

Q . L . L .

w i t h t e m p e r a t u r e . R e g a r d l e s s o f

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C1-516 JOURNAL D E PHYSIQUE

t h e l a r g e v a r i a t i o n o f t h e i n t e n s i t y between -5OC and -lO°C, t h e l i n e width d o e s n o t change v e r y much. T h i s f a c t s u g g e s t s t h a t t h e t h i c k - n e s s o f t h e Q.L.L. changes l a r g e l y w i t h i n t h i s t e m p e r a t u r e range ; however, v e r y s m a l l changes o c c u r i n t h e dynamical p r o p e r t i e s .

I n o u r e x p e r i m e n t , t h e NMR s i g n a l due t o t h e mobile molecules

a t

t h e s u r f a c e was observed even a t a t e m p e r a t u r e o f a s low a s - l O O ° C . This f i n d i n g i n d i c a t e s t h a t some s u r f a c e molecules can r o t a t e a t a much h i g h e r f r e q u e n c y t h a n i n b u l k i c e even a t - l O O e C , however, i t should n o t be c o n s i d e r e d t h a t t h e Q.L.L.

s t i l l

remains a t such a low t e m p e r a t u r e .

The number o f mobile m o l e c u l e s

is

dependent n o t o n l y on t h e tem- p e r a t u r e b u t a l s o on t h e degree of t h e p e r f e c t i o n and t h e c r y s t a l l o g - r a p h i c o r i e n t a t i o n o f t h e s u r f a c e . Our r e s u l t d i f f e r s l a r g e l y from t h e e l l i p s o m e t r i c a l o b s e r v a t i o n (11) o f t h e t e m p e r a t u r e a t which t h e mobile phase a p p e a r s . The d i f f e r e n c e

i s

c a u s e d mainly by t h e d i f f e r - ence i n t h e power o f d e t e c t i o n o f each e x p e r i m e n t a l method t h a n by t h e d i f f e r e n c e i n t h e sample. The q u e s t i o n "how many mobile m o l e c u l e s make t h e s u r f a c e v e r y l i q u i d - l i k e ?I1 can n o t be answered from t h e r e - s u l t s o f o u r experiment u s i n g NMR; however, t h i s method does p r o v i d e i n f o r m a t i o n on t h e s u r f a c e molecule motion.

I t was found t h a t t h e m o l e c u l e s a t t h e s u r f a c e r o t a t e a t

a

f r e - quency o f about f i v e o r d e r s l a r g e r t h a n t h a t o f c r y s t a l l i n e i c e a t t e m p e r a t u r e s between 0 t o -20°C, and t h i s f r e q u e n c y c o r r e s p o n d s t o only a b o u t 1 / 2 5 o f t h a t o f a molecule i n l i q u i d w a t e r .

Regarding d i f f u s i o n by t h e t r a n s l a t i o n a l motion, t h e s u r f a c e mole- c u l e d i f f u s e s

a t

a r a t e o f a b o u t two o r d e r s l a r g e r t h a n t h a t i n b u l k i c e . I t can be concluded t h a t t h e s u r f a c e molecule p o s s e s s e s some p r o p e r t i e s which a r e much c l o s e r t o t h o s e o f l i q u i d w a t e r t h a n t o t h o s e o f c r y s t a l l i n e i c e , b u t t h e y a r e a p p a r e n t l y d i f f e r e n t from t h o s e of l i q u i d w a t e r even a t t e m p e r a t u r e s v e r y c l o s e t o t h e m e l t i n g p o i n t .

The a c t i v a t i o n e n e r g y b o t h f o r t h e r o t a t i o n a l and t h e t r a n s l a - t i o n a l motion o f t h e s u r f a c e molecule a p p e a r t o be l o c a t e d between t h o s e o f l i q u i d w a t e r and c r y s t a l l i n e i c e .

R e f e r e n c e s

Nakaya,U. and Matsumoto,A. U.S.Army Snow,Ice and P e r m a f r o s t Res. R e p t . , 4 (1953) pp 1-6

Wey1,W.A. J . C o l l o i d S c i . , 6 (1951) 389-405

Jellinek,H.H.G. J . C o l l o i d a n 3 I n t e r f a c e S c i . , 25 (1967) 192-205 Fletcher,N.H. P h i l . Mag.,

18

(1968) 1 2 8 7 - 1 z 0

Nason,D. and F l e t c h e r , N . H . J.Chem.Phys.,

62

( 1 9 7 5 ) 4444-4449 G o l e c k i , I . and J a c c a r d , C . J.Phys. C : S o l i d S t a t e Phys.,

11

(1978) 4229-4237

Kvlividze,V.I.,Kiselev,V.F., Kurzaev,A.B. and Ushakova,L.A.

S u r f a c e S c i . ,

9

⁽¹⁹⁷⁴⁾ ^60-68

Anderson,D.M. CRREL Res.Rept., No. 274 (1970) pp 1-17

Bell.J.D.,Mvatt,R.W. and Richards,R.E. Nature, P h y s i c a l S c i . ,

239, .

22 . ( i 9 7 i

j

91-92

Ocampo,J. and K l i n g e r , J . J.Phys. Chem., 87 ( 1 9 8 3 ) 4325-4328 Furukawa,Y., Kuroda,T. and Yamamoto,M. J.>e Physique, T h i s _. -

i s s u e (1987)

Kuroda,T. and Lacmann,R. J . C r y s t a 1 Growth, 56 (1982) 189-205 Abragam,A. i n " The P r i n c i p l e o f Nuclear ~ a g n e E c Resonancet1 Oxford a t t h e Claremdon P r e s s . (1961)

E i s e n b e r g , D . and Kauzmann,W. i n The S t r u c t u r e and P r o p e r t i e s o f Water Oxford Univ. P r e s s . (1969)

Auty,R.P. and Cole,R.H. J.Chem.Phys., 20 (1952) 1309-1314

B u r n e t t , L . J . and Harmon,J.F. J.Chem.phy= 57 ( 1 9 7 2 ) 1293-1297 I t a g a k i , K . J . P h y s . S o c . J a p a n ,

2

(1967) 427-431

Kuhn,W. and Thurkauf,M. Helv. Chim. A c t a ,

2

(1958) 938-971

Ohtomo,M. and Wakahama,G. J.Phys.Chem.,

87

⁽¹⁹⁸³⁾ ^4139-4142

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COMMENTS

E. OFFENBACHER

Can you estimate the thickness of the Q.L.L. from the relative intensity of your signals and your sample parameters

?

Answer

:

Yes I can estimate the thickness of the Q.L.L. by assuming the specific surface area, but in our experiment, especially at higher temperature (-5OC and -lO°C), the surface area reduces by sintering during experiment and further correction is required.

P. PISSIS

I think, it is important for such measurements to have a large surface/volume ratio.

I wonder, in this connection, why you don't use emulsified water droplets where you can easily get droplets of a f e w r m in diameter. Is any reason for not using such systems

?

Answer

:

To obtain the MNR signal due to ice surface, the sample with the larger surface/volume ratio is the better. However the purpose of our study is to know the properties of the quasi-liquid layer between air and crystalline ice.

So we used rather large ice particle but with free outer surface.

P.L.M. PLUMMER

I am very pleased to see your very nice results. My interpretation of your results suggest that since the rotational times of the quasi liquid layer are very similar to those of liquid water but the diffusion times are between those of liquid and solid suggest the layer can also be described as quasi-solid amorphous layer with a high concentration of defects, no long range order and a high degree of rotational freedom. Do you agree and could you amplify on your opinion of the structure of this layer implied by your data

?

Answer

:

Yes. I agree with you basically. We assume that diffusion takes place with molecular unit and we evaluated the spin to spin distance to be about 4 8, so some crystalline structure is expected to be remained in the quasi-liquid layer.

Remark of J.W. GLEN

: