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Anisotropic light scattering spectra and fine wing structure near transition to the mesophase
Journal of
ELSEVIER
MOLECULAR STRUCTURE Journal of Molecular Structure 348 (1995) 201-204
ANrSOTROPIc LIml! scA!cTERING SPEC!‘WANllFINEUINGSTRUC!l!URE NltAR !PRANSI!l!IONTo THE MHX’WSE V.Yu.Lemm,
L.M.Sabirov,
R.L.Sablrov,
T.M.Utartwa
Department, Smkand State Unlvereity, University boulevard, 15, S511~~k5nd 703tlCl4,Uzbekiet5n
Phyeics
In thl5 report the re5ults of studying of the depolarized light 5cattering 5pectra In the ieotroplc phase of nematics and blue phases of cholesterIc are 5hown. 1. The total intexuity 5nd the spectra of Rsyleigh line wing (RW) In the ieotroplc pha8e of the nem8tic liquid crystals PM 5n.dMEW were studied at the experimental eetup with apherlcal interferometer Fabry-Perot 111. The typical spectra for MBl3A 5re ehown in the Flg.1. The time of relazatlon z of the order pararaeter can be determlned only f’rom the halfI(W) width of epectrum of iiie light scatterwith Lorente distribution of the interzeity.Be c8n. be 5een from figure 1. fine AT= ‘7.2” structure of the
FIgare 1. The 5pectra of RI& AT&C-T,. Clearing potit T,= 44.45’C. 0022-2860/95/$09.50 0 1995 Elsevier Science B.V. SSDZ 0022-2860(95)08624-2
All rights reserved
dlcted by de Gennes C21 for
202
liquid
15 observed
cry5tal5,
polarieation. R=2p2/~
connected
Mtroduced liquid
The ehape of
coeffic1ente
coefficient
2 for
received
al50
for
spectral
contour5
PM
1.
Cl
E!iPby
depending
Analogou5
reeult5
of
We
don’t
know any paper
121 deecribe
(CM) by optical
and optical
the cholester1c
in which reeearch
of experBnenta.l
In the BP the total
studied
of
method w5a reported.
We
PurZflcation
been
(BP) between leotropic
feature
myr15tate
8catterMg
on P~IYMEhave
of theory
the blue phaeee
RP of choleeteryl light
out detail-
and appeararrce of WFS to adv5nt5ge.
are ehown the result5
al50
5nd shear
spectrum
laolecular light scattering
report
pha8e of a
Connected with lnteI%CtiOn
pha8e and meeophsee 18 the 5pecifIic cry5tals.
the ieotropic
MBBA.Ba8lc conclusions
The existence
liquid
q v which were
Iwdee.We carried
the 8hape of I(w)
ter R and value
p,
the orientational
Bled translational
of
W
of 5pectra
depend5 on the parameter
to deecr1be
p - viscou8
of orientational
2.
with v1acou8
Here v and ?J are
cry5tal.
ed analysis
the distribution
the latter
by de Cennee
vi5co5itie5,
In
actlvlty
of CM wa8 carried
etudies
In thi8 RI# in the
heterodynu
lnteneity depend-
of
method.
of depolarked on temperature.
out by repeated
recristalli-
n-hexane and rerfuvlng any dust by forcw it through filter with pore dislneter Cl.2 mcmin a cy1lndrUal cell under vacuum. We measured total interrsity on the zation
in the 5olutZon
8ame
experimental
lacer
beam paseed
Latter
allow8
polarization
setup
rametere
of
5pectral
halfwidths
of
of 5cattering
rotation
by polarizer.
of
the
To etudy epectra
of optical light
allow
plane
of
RIX in BP
heterodyning
for
arralogpue one in 141.
to carry
of the optical
through the sample
Pa-
out mea8urementa of
is
activity
8hown in
temperature
behavior
under the angle
of reverse
90’ al80
cp/l
Fig.2.
of the plarre of polarization,
ecattered
but here
In the range from 100 Hz to 50 kHz.
Temperature behavior
the celLThe
of
+O.l’.
spectrometer
the spectrometer
angle of rotation
the ca5e of nem5tic8,
an angle
with accuracy
of beat5
of light
a5 In
to me88ure
analysie
of
the
through the eslaple wa8 analyzed
of CM we resembled
besm paseed
of
for
Here cp - an
1 -the total
laser
diameter interrelty
15 8hown there.
203
88
the
trmsition
fog phase takes place
to
/ 0'
I'
ii=
.-._._.__,_-.IP-
0’ E
v\ . -q
&
5-10 -
lQgure.2.
--,--
II ;’ 1’
f’
P9
/
d
The temperature behavior
of the reverse total interusity and optical activity In the CM.
(&3.6*C+O.O2oC) we csn Bee that optical act~vlty changes it8 84p t0 the opposite and alBo that intensity of light scatterrapidly lncreaBeB (“step” in the de4
passed the throu@ Bsmple snd also modulatlon of light scat-
tering Mtenslty Is observed. Then at the temperature 83.4oCk +O.O2*Cthe Bamplebecome clear, Le. modulation of light scatterInterMAy ends off and dynamic 8peckle8 disappear. The fog phase transits to the BPII. To study the dynamic8 of order parameter fluctuations Zn the isotropic and blue phases of CLCwe registered snd snalyzed 8pectra of the RI& As to the isotropic phase we csn speak more or lees exactly about halfwidth of F&W,because about ltlOoC the one measured by spherical interferometer was approxtitely of 2 MEkand near the trsneitlon to fog phase wan approximately lOtI+ +3tltlkHz. So, far from the pha8e transltlon the resolution of the Bpherical interferomter is already insufficient but near the fog phase halfwidth of the RI# is too broad for our heterodyne spectrometer. In the fog phase slow pulsation of light scattering mtensity dMn‘t allow to measure the halfwidth of RLW. In the Fig.3 are 8hown8pectra of RLWfor BP11 snd RPI regiBteIWdunder two angles of scatterlng. The WYB~B and separation of the Lorentzians were carried out by method of calculating [l/11(& dependenclee. In the range of exietlng of EPII halfwidth of the F&Wis constsnt snd well deecribed by only Lorentzisn with the halfwidth 14.5HM Liz. The titenstty of
204
the RLWaleo i8 colletarrt In thi8 temperature range.Then beg-t r nlng with the temperature 83.15OC, i.e. In the BPI, a new contour with the halfwidth equal to 6.020.5 kHz
Figure 3. The spectra RI# in the blue pha8ee of CM.
with the contour that ~8.8 obaerved m the BPII. The halfwidth of new LorentzMn haen? angular dependence but its contribution to the inten8ity 15 well over for 0=9C0 then for EMlo. The re5ults of 5tudyQlg of
Rl# epectra in the blue phases have been received for the first time 8.8 fsr a5 we know. They carry InformMion on the dynmlc8 of structure5 which fom BP1 and BP11 5nd requZre further consideration uelr& other reeults.
V.Yu.Lerman,
L.M.Sabtiv,
T.M.Utarova, Sov.Phy5. JIBP, 69
(1989) 1151. P.De Gennee, Mol.Cryf3t.Liq.Cry5t. 12(1971) 193. V.A.E!elyakov, A.S.Sonin, Optics of Cholesteric Liquid Cry5tale [in Ru85i5nl,Nauka, Mo5cow, 1982. H.Z.CurmninB, Photon correlation and li.ght beat8pectroacopy, ed. by H.Z.Cumine 8n.dE.R.P&e, PlenumPrees, NewYork and London, 1974, p.287.
ELSEVIER
MOLECULAR STRUCTURE Journal of Molecular Structure 348 (1995) 201-204
ANrSOTROPIc LIml! scA!cTERING SPEC!‘WANllFINEUINGSTRUC!l!URE NltAR !PRANSI!l!IONTo THE MHX’WSE V.Yu.Lemm,
L.M.Sabirov,
R.L.Sablrov,
T.M.Utartwa
Department, Smkand State Unlvereity, University boulevard, 15, S511~~k5nd 703tlCl4,Uzbekiet5n
Phyeics
In thl5 report the re5ults of studying of the depolarized light 5cattering 5pectra In the ieotroplc phase of nematics and blue phases of cholesterIc are 5hown. 1. The total intexuity 5nd the spectra of Rsyleigh line wing (RW) In the ieotroplc pha8e of the nem8tic liquid crystals PM 5n.dMEW were studied at the experimental eetup with apherlcal interferometer Fabry-Perot 111. The typical spectra for MBl3A 5re ehown in the Flg.1. The time of relazatlon z of the order pararaeter can be determlned only f’rom the halfI(W) width of epectrum of iiie light scatterwith Lorente distribution of the interzeity.Be c8n. be 5een from figure 1. fine AT= ‘7.2” structure of the
FIgare 1. The 5pectra of RI& AT&C-T,. Clearing potit T,= 44.45’C. 0022-2860/95/$09.50 0 1995 Elsevier Science B.V. SSDZ 0022-2860(95)08624-2
All rights reserved
dlcted by de Gennes C21 for
202
liquid
15 observed
cry5tal5,
polarieation. R=2p2/~
connected
Mtroduced liquid
The ehape of
coeffic1ente
coefficient
2 for
received
al50
for
spectral
contour5
PM
1.
Cl
E!iPby
depending
Analogou5
reeult5
of
We
don’t
know any paper
121 deecribe
(CM) by optical
and optical
the cholester1c
in which reeearch
of experBnenta.l
In the BP the total
studied
of
method w5a reported.
We
PurZflcation
been
(BP) between leotropic
feature
myr15tate
8catterMg
on P~IYMEhave
of theory
the blue phaeee
RP of choleeteryl light
out detail-
and appeararrce of WFS to adv5nt5ge.
are ehown the result5
al50
5nd shear
spectrum
laolecular light scattering
report
pha8e of a
Connected with lnteI%CtiOn
pha8e and meeophsee 18 the 5pecifIic cry5tals.
the ieotropic
MBBA.Ba8lc conclusions
The existence
liquid
q v which were
Iwdee.We carried
the 8hape of I(w)
ter R and value
p,
the orientational
Bled translational
of
W
of 5pectra
depend5 on the parameter
to deecr1be
p - viscou8
of orientational
2.
with v1acou8
Here v and ?J are
cry5tal.
ed analysis
the distribution
the latter
by de Cennee
vi5co5itie5,
In
actlvlty
of CM wa8 carried
etudies
In thi8 RI# in the
heterodynu
lnteneity depend-
of
method.
of depolarked on temperature.
out by repeated
recristalli-
n-hexane and rerfuvlng any dust by forcw it through filter with pore dislneter Cl.2 mcmin a cy1lndrUal cell under vacuum. We measured total interrsity on the zation
in the 5olutZon
8ame
experimental
lacer
beam paseed
Latter
allow8
polarization
setup
rametere
of
5pectral
halfwidths
of
of 5cattering
rotation
by polarizer.
of
the
To etudy epectra
of optical light
allow
plane
of
RIX in BP
heterodyning
for
arralogpue one in 141.
to carry
of the optical
through the sample
Pa-
out mea8urementa of
is
activity
8hown in
temperature
behavior
under the angle
of reverse
90’ al80
cp/l
Fig.2.
of the plarre of polarization,
ecattered
but here
In the range from 100 Hz to 50 kHz.
Temperature behavior
the celLThe
of
+O.l’.
spectrometer
the spectrometer
angle of rotation
the ca5e of nem5tic8,
an angle
with accuracy
of beat5
of light
a5 In
to me88ure
analysie
of
the
through the eslaple wa8 analyzed
of CM we resembled
besm paseed
of
for
Here cp - an
1 -the total
laser
diameter interrelty
15 8hown there.
203
88
the
trmsition
fog phase takes place
to
/ 0'
I'
ii=
.-._._.__,_-.IP-
0’ E
v\ . -q
&
5-10 -
lQgure.2.
--,--
II ;’ 1’
f’
P9
/
d
The temperature behavior
of the reverse total interusity and optical activity In the CM.
(&3.6*C+O.O2oC) we csn Bee that optical act~vlty changes it8 84p t0 the opposite and alBo that intensity of light scatterrapidly lncreaBeB (“step” in the de4
passed the throu@ Bsmple snd also modulatlon of light scat-
tering Mtenslty Is observed. Then at the temperature 83.4oCk +O.O2*Cthe Bamplebecome clear, Le. modulation of light scatterInterMAy ends off and dynamic 8peckle8 disappear. The fog phase transits to the BPII. To study the dynamic8 of order parameter fluctuations Zn the isotropic and blue phases of CLCwe registered snd snalyzed 8pectra of the RI& As to the isotropic phase we csn speak more or lees exactly about halfwidth of F&W,because about ltlOoC the one measured by spherical interferometer was approxtitely of 2 MEkand near the trsneitlon to fog phase wan approximately lOtI+ +3tltlkHz. So, far from the pha8e transltlon the resolution of the Bpherical interferomter is already insufficient but near the fog phase halfwidth of the RI# is too broad for our heterodyne spectrometer. In the fog phase slow pulsation of light scattering mtensity dMn‘t allow to measure the halfwidth of RLW. In the Fig.3 are 8hown8pectra of RLWfor BP11 snd RPI regiBteIWdunder two angles of scatterlng. The WYB~B and separation of the Lorentzians were carried out by method of calculating [l/11(& dependenclee. In the range of exietlng of EPII halfwidth of the F&Wis constsnt snd well deecribed by only Lorentzisn with the halfwidth 14.5HM Liz. The titenstty of
204
the RLWaleo i8 colletarrt In thi8 temperature range.Then beg-t r nlng with the temperature 83.15OC, i.e. In the BPI, a new contour with the halfwidth equal to 6.020.5 kHz
Figure 3. The spectra RI# in the blue pha8ee of CM.
with the contour that ~8.8 obaerved m the BPII. The halfwidth of new LorentzMn haen? angular dependence but its contribution to the inten8ity 15 well over for 0=9C0 then for EMlo. The re5ults of 5tudyQlg of
Rl# epectra in the blue phases have been received for the first time 8.8 fsr a5 we know. They carry InformMion on the dynmlc8 of structure5 which fom BP1 and BP11 5nd requZre further consideration uelr& other reeults.
V.Yu.Lerman,
L.M.Sabtiv,
T.M.Utarova, Sov.Phy5. JIBP, 69
(1989) 1151. P.De Gennee, Mol.Cryf3t.Liq.Cry5t. 12(1971) 193. V.A.E!elyakov, A.S.Sonin, Optics of Cholesteric Liquid Cry5tale [in Ru85i5nl,Nauka, Mo5cow, 1982. H.Z.CurmninB, Photon correlation and li.ght beat8pectroacopy, ed. by H.Z.Cumine 8n.dE.R.P&e, PlenumPrees, NewYork and London, 1974, p.287.