RESULTS OF MEASUREMENTS OF SPIN LATTICE RELAZATION TIMES IN LIQUIDS OBTAINED IN THE CRACOW LABORATORY OF NUCLEAR MAGNETIC RESONANCE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A005400040001-7
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 10
• Document Creation Date: December 22, 2016
• Document Release Date: July 9, 2009
• Sequence Number: 1
• Publication Date: January 12, 1959
• Content Type: REPORT

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RESULTS OF MEASUREMENTS OF SPIN LATTICE RELAXATION TIMES IN LIQUIDS
OBTAINED TN THE CRACOW LABORATORY OF NUCLEAR MAGNETIC RESONANCE
Nuclear Resonance Laboratory of the Institute of Nuclear Researchq
Polish Academy of Sciences, Cracow.
The preliminary results of the investigation of spin-lattice rela-
xation times in liquids obtdn*d in the Cracow Laboratory of the Nuclear
Magnetic Resonance are described. We used the metod of measurements
presented in the previous communication by Hennel and Hrynkiewicz.
The Bloembergen. Purcell and Pound theory of the spin-lattice
relaxation times /l/ gave for ours water at 200 C T 1 . 3*4 sec.
When to their calculation the correction made by Kubo and Tomita /2/
is introduced and when the newest values of atomic constants are used
the theoretical value of T 1 for water amounts 2*5 sec. As it is well
known this value must be regarded as an approximate one because of the
simplifications of the model on which base the theory of relaxation
times is developed.
The experimental val,.;ee published-by Giulotto and collaborators
for water at 20 0 C caref'uly purified from oxygen are /3'6 1 0'2/ see /3/
/3*5 1 0'35/ see /4/ and 3*1 sec /5/.
In our measurement$ we used several samples of water sealed in
glass and quartz tubes. The water was very carefuly purified by a
chemical method. made oxygen free by long boiling and sealed in vacuum.
Our result at 200C is /3*21 1 0*07/sec.
On the last Colloque AMPERE Giulotto presented the temperature dependence
of the water relaxation time T I He obtained a slow decrease of the
expression 7 T I /T with increasing temperature, while the BPP theory
predicts the constant value of this expression. We obtained the similar
dependence as found by Giulotto-. The results are represented on Fig.l.
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I.
?
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IV W- QF
Fig.2. Temperature dependence of T 1 for water solutions or gelatin.
For calculation of 7 T I /T expressions the viscosity of a pure
water was taken. It is clearly seen from the diagram , that I T 1 /T
calculated in this manner is nearly constant over a rather wide range
of temperatures. It means that though the macroviscosity of the gelatin
solution changes much more than that of water. the relaxation in water
in governed by its own viscosity. It is worthwhile to notice that at
the melting point of gelatin, where is a big jump of the macroviscoaity,
no jump of T 1 can be observed. The shift of curves t, lower values for
more concentrbed solutions is caused by paramagnetic impurities contained
in gelatin. Our results prove that for investgated concentrations the
main part of water molecules can be regarded as free filling the cavities
between gelatin molecules.
References
2. R. Kubo, K. Tomitm. J. Phys.Soc. Japan, 2. 888 /1954/.
6. X.J. Selden, C.R,Acad.Sci./Paris/. L12. 1614 /1957/
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Muclear Resonance Laboratory of the Institute of Nuclear Research.
Polish Academy of Sciences. Cracow.
In the few lost years the question of nuclear spin-lattice relaxation
time T I of liquids became important in spite of its significance as &
means for investigation of the structure of liquidsIn this situation
the problem of the method of precision measurements of T I in very actual.
Till now the methods most frequently used 1 are:
/I/ the direct method. 121 the progressive saturation method. /3/ the
method worked out by L. Giulotto and coll.(21based on the Bloch's adiabatic
rapid passage.
The direct method relies on observa*tion of the growth'of the nuclear
resonance line that has been satui-ated before. During the observation the
high frequency magnetic field H 1 should be small enough to additional
saturation. The accuracy of this method is rather a low one. Bloombergon(3]
Purcell and Pound estimate the error of their measurement of T 1 in water
at 200C for 20 per cent.
The progressive saturation method gives only the posibility of the
measurement of the ratio of spin-lattice relaxation times T I for two
samples. So It can be used only in connection with another absolute method.
The progressive saturation method in especially convenient for measurements
of short relaxatlon times.
The most exact method known till now Is the Giulotto method [21
7t depends on measurement of the height of resonance lines for different
time Intervals between the adiabatic passage* through the resonance
conditions. Tf a correct value 'of the spin lattice relaxation time in to
be obtained the following conditions must be fulfiled
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Where 6' - gyromagnetic ratio of the nunleue
H m - modulating magnetic field amplitude
W m - circular frequency of the modulating magnetic field
T 1 - spin-lattice nuclear relaxation time
fulfilment
The difficulty in this method comes from the fact that the simultaneous
of conditions mentioned above often causes great difficulties of rractical
nature. E.g. if T 2.35 sec. I and is lemanded all inequalitles
and the modulation field lim-LOG gaussc Practically it is very difficult
to obtain such 8 high modulation field in a gap of ;,n electromagnet,
To overcome the difficulties mentioned abnve a following method
was workeJ out. The measurement of spin-lattice relaxation time of liquid
sample consists of two separate parts: the measurement of the completely
desaturated nuclear magnetization Kand the measurement cf the momentary
values of the vector V during the time of his growth from zero after a
complete saturation.
The nuclear magnetic resonance device Is arranged in such a way that
it is possible to change alternatively the frequency of the current in
the modulating coils. This can be done by means of a single switch. The
used magnetic field modulations are W, m - 2T 50 sec- 1
H;-2 gause and W M.27 - 0.3 sec- 1 Hm.6 gauss. This last type of
modulation is made by means of an electrolytic potentiometer (2) moved
by an electric motor. Mhen the motor is not running it is possible to
set the rotating electrode of the potentiometer in the desired position.
The output of the nuclear resonance detecting apparatus is recorded
on a photographic paper tape by means of a mirror oscillograph.
The course of the magnetic field modulation is shown on fig.l.
The central vaiu. of the magnetic field is oxactly the resonance one Ho.
At first the rotating electrode of the electrolytic modulator Is set in
one of Its extreme position. /e.g. the lower one/ and the higher frequency
modulation current Is switched on. If the proper value of the radio
!rejj~ncy -nhgretir field H I Is used the sample is completely saturated
time rmrikp ver C.7 - VT ser. iOVhPn the lines lo not disappear completely
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in spite of the phase memory about 5% /in amplitude/ of about 30 c
modulation was added to the 50 c.p,e. modulation for destruction o;pt:
memory. I
1TILLLLLI
E
rig. 1 Method of T 1 measurement, a - magnetic field vs. time,
b - record of the mirror oscillograph.
After the sample is completely saturated by means of the 50 c.p.s.
modulation the switch is turned to the second position and the modulation
coils are conected with the electrolytic potentiometer. In this moment
t on figure l/ the magnetic field intensity jumps to the lower extreme
value because of the initial position of the rotating electrode. Since
this time the sample is very far away from the resonance conditions and
the growth of the nuclear magnetization goes without external perturbation.
?he next passage through the resonance value /moment t 3 / can be made by
setting in motion the electrolytic modulator in a suitable chosen moment t..
If the time interval t 3- t 1 /i.e. the free growth time/ is suffitiently
long t 3- t I > 5T 1 the height of the recorded line is proportional to the
completely deasturated value of the nuclear magnetization 1. . The momentary
values of magnetization vector 9 during its growth can be cUtained by
chosing a shorten time interval t 3 - ti. We evaluated that the best accuracy
can be obtained if 0,6 T I ec t 3 - t I < 1.5T 11 The most practical way in
to make one U - record. immediately three or f(ur K records and then one
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N - record again. The &quality of both V- indicates that the amplificatt
factor did not change during the whole measurement.
The measurement of the t 3 - t 1 time can be done by means of the sto
clock if this is a long one. In the case of short time intervals the
measurement can be done using the time marks /A on fig.l/. Then the mirro
oscillograph must have three separate mirror devices: for the output
record /C/. for the time marks /A/ and for the t I moment record /B/. This
last mirror device in connected with the 50 c.p.s. modulation circuit.
The evaluation of T 1 from the date obtained in this munner is done
by means of a plot - In /1-M/Z- / versus t 3 - t I /fig. 21.
It is also very useful to make a control diagram of exp/-t/T I / vers
9 putting for T 1 the obtained value /fig.3/. If the measurement is correc
all points should lie on a straight line /of course if the sample obeyed
the single exponential increase law/ which intersects the vertical axis
in point I and the horizontal axis in point V Even a small error in
N - can be found this way.
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Fig- 3. Control diagram for W.
Using the described method it is Possible to observe the nuclear
relaxation process phenomenon with lower than in other methods pertutbation,
introduced by the nuclear resonance apparatus. This comes from the fact
that using the other methods it is necessary to fulfil several conditions
knentioned above/ which practically are difficult or even not possible to
satisfy simultaneously.
Using the described method it is necessary to fulfil only tree
conditions which do not cause technical diffieulties. These conditions are:
The time of passage T 4: T 1 where 't -
N
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The described method in comparison with Giulotto'a does not require
the fulfilment of the adiabatic passage condition /l/ and the condition
Our method was Succesfully used in Cracow laboratory for Lneanuremente
of spin-lattice relaxation times in liquids over the range 0.5 - 100 sec.
The accurancy of measurement of T l' for pure water in 200C in estimated
as less than 3 per cent.
1. Andrew E.R.. Nuclear Magnetic Resonance, Cambridge 1955, P-107
Nucvo Cimento 1_2. 519 /1954/
3. Bloembergen F.. E.g. Purcell. R.V. Pound. Phye.Rev.. U, 679 /1948/
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