••

Ind ian Journal of Pure & Appli ed Ph y~ic~ Vol. 3X. May 2()OO. pp. 335-343

Raman and Brillouin scattering studies on liquids and solids using an ultra high resolution spectrometer

L P Sarma & T N Gowd

Nat iona l Geophysicn l Research Institute, Hyderabad 500 007

Recei ved 19 January 2000: accepted IS M arch 2000

Use or a statc or thc art ultra high resolution spectrometer (0.04 cm- I) for both Ramnn and Brill ouin scnttering studies on

liquids and sol ids hns becn reported. The spectrometer calihmted with mercury lines hns been standardized by resolving the

isotopes or chlorine in the v I Raman mode of enrbon tetrachloride (CCI4). The spectm of Doppler shifted Brill ouin doublets and

cent ra l Ray leigh l ine for ~ome molecular liquids: cnrbon tetrachloride (CCl4). ult ra pure water (H20 ). ethanol (C2H"OH).

methanol (CH, OH). propanol ((CH,)2Ci-IOH). methylhutane ((C H,hCH.CH.CH,). amylacetate (CH, COOC, H I I)' hydrogen

perox ide (H20 2) and in natu ra l mi neral~: hydrous quartz (Si02.IlH20) and gypsum (CaS04.2 H20) have been recorded and

presen ted. The resul ts demonst rate that the Bril louin doublets and the centml Rayleigh l ine have heen wel l re~o l ved 1'01' their

line shifl. in tensi ty and hackground. Sou nd veloc iti es (VI) and sound absorption (IR/2 /B) cnlculated fro m the Brillouin shi ft and

thc integrated intensities of the Ray leigh and Brillou in doublets are compared wi th the available publi shed data. The discrepnncies

hetween the measured Vand IR/2 /1l (Landau and Placzek rati o) and those reported in the literature have heen attributed mainly

to velocity dispersion and thermodynamic dispersion respectively. In some of the liquids. a considerable part of the tota l intensity

has heen found to be in the background under the Ray leigh- Brillouin components indicat ing the presence of new mode. Further

spectral analys is are in progress to identify t he~e modes. From these measurements. the authors found that the ultrahigh

resol ution spectrometer is unique for carry ing out Raman. Brillou in nnd Rayleigh scattering stu dies on l iqu ids and solids alike.

1 Introduction The ad vent of laser techno logy has s implifi ed spec­

troscopi c techniques to a g reat ex tent and a large part of

the researc h efforts has been in the fie ld o f li ght scatte r­

in g studies on liquids, so lids and thin f ilms. Sound

absorpti on in liquids can be ex pl a ined on the bas is of

thermodynami c pa rameter y and viscos ity 11 and can be

treated as fundamental the rmodynamic properties of

liquids. Even though ultrasonic methods made the Cp,

Cv and y measurements eas ie r, appropri ate explanati ons

fo r the variati on in suc h fundamenta l properti es have

been from the Brill ouin scatte ring meas urements us ing

the re lat ion o f Landau and Pl aczek I. The line shift, width

and bac kground in the Ray le igh and Brillouin spectra

have conside rable s ignificance in unde rstanding the re­

laxation mechanis ms in liquids . To outline a few, an

intense broad background in the reported Brillouin spec­

trum2 of CC I4 agrees we ll with the thermal re laxati on

theory of Mounta in . A weak coupling between the

inte rna l vibrati onal degrees of freedo m and translat iona l

degrees of freedom sugges ted a s ing le re laxation time'

in C6Hh and CS 2. It has been reported that the agreement

be tween the observed and the calculated Brill ouin fre-

que ncy shi fts seems to be qui te sati sfacto ry ignoring the

di spe rsion of veloc ity w ith freque nc/. Recent stud ies

are on the e lastic constants of the metasta bl e o rie ntat ion­

a lly di sorde red phase of CC I4 and on C Br.\ by Zuk el

aL5.6

. Studies near the triple po int of sulphur hexafluoride

(SF6) at 22 1 K indicated that SF6 possesses a plasti c

phase as refl ected in its e lasto-optic coeff ic ients 7

Brillouin spectroscopic studies on solids a re o riented

ma inly to understand the e lasti c be hav iour as a funct ion

o f struc ture, compos itio n, pressure and temperature.

E lasti c moduli di stingui shed the ro les o f composit ion

and c rysta l struc ture in several s ing le c rysta l s ili catesK•

Brill ouin scatte ring technique has been wide ly used to

measure e lasti c moduli at hi gh pressuresY• Brill ouin

measurements on gases such as /1 - H2 and /1- D2 at O.S and 10

20 GPa pressure range have also been reported . The

transition of H 20 to symmetric ice ( ice X) at and above

70 GPa has been reported using Brill ouin spectros­

copy II. Other studies inc lude the measurement of refrac­

ti ve index and e lastic properti es of a s ingle crysta l

corundum (a-AhO,) up to a te mpe rature l2 of 2 100 K.

Inte resting studies are e last ic moduli on chemi ca l va­

pour depos ited (CYD) polyc rystalline di amond and the

INDJA 1 PURE & APPL PHYS, VOL 38, MA Y 2000

detection of a surface Rayleigh model ' . Another recent work is on acoustic wa ve velocities in two glasses at high pressures and temperature for a sharp turnin g point in the ve loc ity- temperature plots indicating the glass transiti on temperature 1-1. The Brillouin spectroscopic studies leading to the computat ion of elast ic properties on hydrous minerals li ke quartz (S i0 2.nH 20) and gy p­sum (CaS04.2H20 ) aSSllmes great significance as the configurati on of fluid s into the mineral matri x intlu­ences the physical and thermody nam ic properti es re­fl ec ting the processes in the earth ' s inte ri or. In all these studies a basic Fabry- Perot interfero meter has been used with appropriate changes incorporated in the instrumen­tation for a spec ific application. The present study de­scribes an ex perimental set-up, utilizing a state of the art ultrahi gh resolution monochromator that can be used for Raman , Brill ouin and Ra yle igh scattering measure­ments in liquids and so li ds alike.

2 Brillouin Scattering Brill ouin l' scatterin g is the inelast ic scattering of

I ight from an acoust ic phonon and is considered as a spec if ic type of first order Raman scattering. An incident

photon with wave vector and frequency ki and Wi respec­ti ve ly and scattered by a thermal phonon will obta in a

new wave vec tor and frequency k, and W , . Ex perimen­

ta ll y ki , k, and Wi can be de termined if a monochromatic

light source (AI) is used to illuminate the sampl e and the scat tered li ght is observed in a specifi ed d irection Vas

shown in Fig. I. Then the meas urement of W, is suffici ent to dete rmine the phonon veloc ities (VI) in liqu ids and solids as per the generali zed express ion for Brillouin

shift (L'lWII) of the scattered light: 2 11 V si n ( <p/2 )

±~WI\ = (ws - Wi) = . . .. ( I) Ie I ("

where 11 is the refraCt ive index, (~, the :--cattering an gle,

lei the wave length of light ami V the acoustic wave \'e locitv. The + si!:'"n corresDonds to anti slOkes and- sign

I I : 0 : k; [>--s, ws] h-I , ,) I V I I I I I ~ >--l~

[>--l,WlJ !7[>--l,Wl]

Fi~. I - Schell1 ali c ()I ' SC<\IIL:ril1~ pilCIHlIllCII()1l

to stokes lines. Because of the Doppler effect , the Bril ­

louin shift is e9ual to the frequency WI of the longitudi nal . 6· h d' acoustic wave In t e me lum :

L'lWI3 = WI The acousti c wave ve loc ity V is ca lculated from Eq.

( I). Also, 'Y the ratio of the Intensity of the Rayleigh component to the sum of the two Bri II u in component. · can be obtai ned from Eq. (2):

IR /2 /13 =CI' / Cv - I ='Y ... (2)

This is popularl y known as the Landau-Placzek ratio l6.

The above re lati on shows that the in tens ity of Rayleigh scattering is proportiona l to CI'-CV and to a good approx imation , line shapes fo r both Rayleigh and Brillouin are considered to be Lorentzian '7 .

3 Experimental Details An ultrahi gh reso luti on laser spectrometer (SO­

PRA,DMDP-2000 Model) has been employed to carry out the Raman and Bri ll ouin s pe~troscopi c measure­ments of liquids and solids in the present study . Till:

SOPRA, DMDP-2000 mode l is a unique instrument or totally new concept in the worl d of monochromators with the capabilities of hi gh resolution. lum inosity. con­trast, prec ision and flex ibility. A sc hemati c repre­se nt a t io n of th e u ltrah ig h reso luti o n I cl.~er

monoc hromator setup L1sed for Raman spectroscopic stud ies on gypsum lX is shown in Fig . 2. The ex perimen­tal arran ge ment utilize~ a temperature stab ili zed eral oll that was opt ically coupled in the cavity of a 514,5 nm , and 5W Ar+ ion laser to obtain a narrow mono mode lillc of minimum width. Air spaced etalon is preferred for" stable frequency , operating at the two high gain argon lines of 488.0 and 514.5 nm, The 514.5 nm laser beam. after due filte ring of the plasma lines through the Pho­tophysics fi Iter 1110nochromaror, is made to focus on the sample with a planocollvex lens of focal length 60 mJ11

at 9()O scattering geollletry . The :--cattered radIation fl"'llll

th~ sample (generally I in W {) parts ) I~ co llected by <Ill achromatic lens of 50 n llll foca l length. After collimal­ing the beam through an adjustable aperture, it is con­verged by another achromatic lens of 250 111m focal length and then is focussed on to the entrance slit SI,

opened to 20 ~ll11, of the SOPRA DMDP-2000 mono­chromator. The SOPRA, DMDP-2000 monochromator. of 2m length can be conveniently configu red for both double pass and single pas~ operati on. The ultrahi~h resoluti on of 0 .02 em- I in the Ill ' nuc hrnmator i\

ach ieved through the double monochromator double

,.4-

SARMA & GOWD: RAMAN & BRILLOUIN SCATTERI NG USING SPECTROM ETER 337

pass (DMDP) configuration while the doubl e mono­chromator single pass (DMSP) configuration g ives a resolution of OJl4 e m- I. Two hi gh resolution eche ll e

gratings( 220 x I 10 mm, with 3 16 grooves/mm ) ar­ranged in the monochromator are responsible for the ultrahi gh resoluti on. In the DMDP mode, the radiation

effect ive ly trave ls a distance of "" 32 m. while in DMSP

it is "" 16 m. The arrows in the schematic of Fig. 2. shows the direction of the ray path in the first monochromator

and a replica of the ray path in the second monoch roma­tor of equivalent configuration . The refl ected radiati on from the rear mirror M2 eventuall y reaches the detector that is foc ussed to the e xit slit S" w ith a opening of 3()

11m. The entrance (SI ), inte rmediate IS and the exit S] are graduated curved s lits ancl can be opened and c losed

to ± 5 11m from 10 to 3000 ~lm . T he incident ang le on the grating is given by :

2 sin (i) .cos (E) = k.N./.... 1O-6

~t3- -~-- ----~~B 1

l1UJ

A - - - --'

, I :

I -or

I I 5A

I L_ b

d

c 58

~e 1-- ...

~ :> g

Fi g. 2 - Schematic of the li ght scattcring apparatus: I . Ar+ ion laser (wavelength = 514.5 nm). 2. TempcraLure stabili zed eta lon. 3. Filter

monochromator. 4. Pre-entrance optical arrangement : a. Planoconvex lens (F 60 mm. <I> = 30.0 mm). b. Sample holding prism table

(F 60 mm. <I> = 25.4 mm). c. Achromati c lens assembly collection collimating. d. Iris diaphragm. e. Achromati c lens (F 250 mm. El = 31.5

mm). r. Total rell ection pri sm assemhly . g. 1J2 platc holder. h. Entrance slit (S d. 5. Monochrometer (SOPRA. DMDP- 2(00): SA .

a. Echelon graIing (G I ) . h.Rem Mirror (M I l. c. Tota l reflcction pri sm. d. Intermediatc slit (IS). 5B. c. Rear Mirror (M 2). r. Grating (G]) .

g. Ex it slit (S2) . h. PhOIO multiplier tube (PMT)

33X INDIAN J PURE & APPL PHYS, VOL 38, MAY 2000

where £ is the ebert angle, k the order number, N the

number of grooves (316/mm) and A (514.5 nm) the wave length in nm. In order to achieve ultra high reso­

lution, high angle of incidence (63.5°), a long focal

distance, very large gratings (I lOx 220 mm), a slit width

of 20/20120 !lm and a slit height of up to 20 mm have been chosen.

For operation at A = 514.5 nm in the II th order (k =

II) the dispersion in DMDP mode is 0.016 nm/mm, while in DMSP mode, it is 0.021 nmlmm. The optical alignments within the monochromator are checked with extreme care as 11th order ray is to traverse a distance

of 16m in the DMSP mode. The gratings with N = 316

grooves/mm, at the Blaze angle of 63°26' and the Blaze

wavelength of 5.658 !lm have maximum reflectance in its 11th order. As a result, a maximum of 90 % of the theoretical resolution has been achieved in separating the hyperfine lines of mercury of 4358 A.

The gratings are positioned by a stepper motor drive to any required wave number within the free spectral range (FSR) up to 1800 cm- I in the II th order of its operation. The stepper motor drive is controlled by a PC with a DMDP software facilitating the operation of the instrument either in temporal scan mode for enhancing the signal quality at any fixed position of the gratings or in the wave length scan mode for acquiring the spectro­metric data. A photo-multiplier tube (PMT) fixed at the exit slit S4 detects and counts the photons reaching the PMT in a given interval of time for a given step rate. The photoelectrons from the PMT are sent to a processor for integration and display on the computer terminal. The

advantage with this system is that PMT permits the main line to be scanned through, a basic requirement for Brillouin spectroscopy .

After proper al ignment of the pre-entrance optics and the ray path height in the monochromator as well as the gratings, the monochromator is set for either DMDP or DMSP configuration. A thick wall ed rectangular quartz

cell (10 mm x 10 mm x 50 111m) containing the liquid sample is placed on the pri sm table with an option to rotate the sample cell to a fraction of a degree marked on a circular scale.

The liquid sample in the cell irradiated with an Ar+ ion 514.5 nm laser beam 01'200 mW power, the scattered light focussed on to the entrance slit S I partially opened

("" 30 m for Brillouin and 200 !lIn for Raman) is then scanned in the wave number region of interest up to 1800 cm- I

. The advantage of SOPRA DMDP-2000 is that it

allows the scanning through the main line thereby ena­bling an access to low frequency Raman (external modes), central Rayleigh and the Doppler shifted Bril­louin components. Further, by placing a temperature stabilized etalon in the laser cavity, it has been possible to narrow down the line width thereby extending its adaptability for Rayleigh Brillouin (RB) scattering stud­ies, while retaining all the features required for an ultra high resolution Raman spectrometer. The scattering ge­

ometry (90°) and the wave length ( A = 514.5 nm) of the laser light determine the wave vector of the acoustic

phonons under study. A deflection of 0.5° from the

normal (90°) scattering geometry resulted in an ambigu­

ity of "" 0 .005 cm- I shift in the Brillouin component peaks.

4 Results and Discussion In the present study, pure component liquids: carbon

tetrachloride (CCI4), ultra pure water (H20), ethanol (C2HsOH), methanol (CH30H), propanol ( (CH3) 2.

CHOH), methyl butane «CH3)2 CH.CH.CH3 ), amyl acetate (CH3 COOCSH II ), and hydrogen peroxide (H20 2), and natural hydrous minerals; gyp­sum(CaS04.2H20) and quartz ( Si02.nH20) have been investigated for acoustic velocities and absorption using Raman, Brillouin and Rayleigh scattering technique ~ .

Raman spectra of CCI4 (Fig. 3) shows the well known

Raman lines at 459.4 cm- l(vl), 218 .9 cm- l(v2) and 3IS.X

cm- I (V4) . The inset, zoomed view of the V I mode, clearly

shows the Raman lines corresponding to the well re-

I d . f hi' (CI 1S CI 3sCI37 CI 35 so ve Isotopes 0 c onne 4 ' , 3 , 2 CI2 37)1~ implying that the instrument is standardized for

acquiring a high quality spectroscopic data. The Brillouin spectra (as acquired) for ultra pure

water is presented in Fig. 4. The figure shows well developed Brillouin doublets located symmetricall y about the unshiftcd central Rayleigh line and are clearl y separated by (l.20 cm- I

. From the Brillouin spectra (Fi g. S) , the Brillouin shifts for carbon tetrachloride, am) ­lacetate, methylbutane and propanol have been found to be 0.120,0.150, 0.112 and 0.131 cm- I respectively .

Similarly, Brillouin shifts (.0.0)13) for benzene, hydrogen peroxide, ethanol and methanol have been 0.206, 0.200, 0. 145, and 0.141 cm- I respectively as seen from Fig. 6. Smooth curves in the spectra are Lorentzian fits to the experimental data using LAB CALC software (Galactic Corporation , USA) . The Brillouin spectra as acquired on a natural hydrous quartz (Fig. 7) indicates that the Brillouin components for longitudinal (LA) and trans-

SARMA & GOWD: RAMAN & BRILLOU IN SCATIERING USING SPECTROMETER 339

verse (T A) acousti c modes are well resol ved wi th ~(J) II

of 0.80 and 0.50 cm- I respect ively. Similarl y, the Bril­louin shi fts for the LA and T A modes fo r natural gypsum in (0 I 0) direct ion have been fo und to be 0.72 and 0.49 cm- I respectively (Fig. 8). In tensities of Ray leigh peak in both these mineral specimens were found to be many folds higher than that of the Brill ouin components and hence the former was masked using a neutra l density

filter in order to highli ght the later (Brillouin peaks). The observed Brillouin shifts fo r liquids and solids are pre­sented in Table I along with specific grav ity and refrac­tiv e index . Aco usti c wave ve loc ities have bee n calculated as per Eq. ( I ) from these va lues of the Bril ­louin shi fts and the same are presented in Tab le I . These veloc ity values determi ned are compared with those reported by others and those from standard tables. A

40000,---------------------------------~

r<> 0

~ c:: :J

>-~

0

..0 ~

0 ........ >-

(j)

c OJ

-=

<f)

-C :=J

>-~

CJ ~

.-

.D ~

CJ ........ :>..

<f)

c (]) -c

30000

200 0 0

10000

0

lCl (\J

to <j"

I I

-500 -450 - 4 00 -350 - 3 0 0 - 250

Wav e num bers! (C m- 1 )

12· 20

6·10

- 0 ·2 0 1· 23

-0 ,50 -0 ·30 -0,10 0 ·1 0 0 · 3 0

Br ill ou in Shifts/cm- I

Fig. 4 - Bri ll ouin spectra of ul tra pll re water (H20 ) (as acquired)

a> 00 (\J

I I

- 200

0 ·50

:l4 () INDIA J PURE & APPL PHYS, VOL 3X, MAY 200()

9 1 a CCl 4

b \{) CH3 COOC5 HII ('1') 69 0 \{)

If)

46 N

Y N

C ::::J

>- 23 .... J 0 .... 0 -

-D 72 I >- N

(CH3)2CH.CH.CH3 d (CH3)2CH OH 0 C -:-

.......... 54 N

>-!2

If) 36 0 c I <l>

J c 18 _ /J

0 -0'20 0 0 ·20 -0,20 0 0·20

Brillouin -1

Shift / em

Fig . .'i - Brilloui n spectra of l iqu ids: a. Carbon tetrachloride (CCl4) . h. A mylacetate (CH,COOC5 H II), c. M ethyl bu ta ne

(CH3)2C HCH-CHl ). d. Propanol ((CH3hCHOH). Smooth l ine shows the Lorelllzian curve f itt ing for the ra" spectra

08 (0 )

C6 H6 ( b ) H2 02 1"0 81 0

(/) 54 0

c: N 0

:::J 0 N

>- 27 I 6

>- '-. 0

0 ......

52 .D >- (C) C2 H5OH (d) _CH3OH 0 o;t

'-- 114 10 <t"

I :! :::-

If) 76

I c: (l)

c: 38

~ 0 -0·30 Q 0 ·30 -0-30 0 0 ·30

Brillouin Shift / cm-!

Fig . () - Bril lou in spectra o f liqu ids: a. Benzene (C6H6), b. Hydrogen peroxide (H20 1). c. EthaI10 l (C2H:;0 H). d. Melhanol (CH30 H). Smooth linc shows the Lorentzinn curve fitt ing for the raw spectra

--

....

SARMA & GOWD: RAMAN & BRILLOUI SCAlTERING USING SPECTROMETER 34 1

r<> 0

.!'2 c ~

::-2

-Cl ~

0 ....... >-

V> c <1>

~

r<l 0

~ .-<..: ::>

>-~

~

-Cl ~

0 .......

.-V> C <L>

~

35·00 0

26 25

17 ·50 LA

LA

8 ·75

0 -/-4 1·4

37·00 b Notural Gypsum

2775 TA

TA

18·50

9·25

0 - 3·0 - 1,5 0 1 5 3·0

- 1 Bri lloui n Shif f /cm

Fii:! . 7 - Brillouin spectra or a. quanz and h. gypsuill silowill!,! L A ;1I1d TA l110des

small but a defin ite differe llce in the velocity values of these liquids coul d be attributed to ve loc ity di spers ion and to the puri ty grade of these liquids .

The experimen tall y observed La ndau and Placzek intensity ratio (iR/211\) for some of the molecular liquids uncorrected for depolarization due to inelastic scattering ha:-- also been presented III Table I. Rayle igh intensi ty (lId i~ proportional to (C1,-C v) and one weakness that arises out of the intens ity ratios is the neglect of di sper­sion in the thermodynamic properli es, since the intensi­ties (II I) arc measured at re la tively hi gher freq uencies . From the spectra it is fo und lhal the Landau and Placzek ratio of H20 and H20 } is much greater than 2.0 even though the Bri llouin sh ifts correspond to the literature values. For other liqu ids. in particul ar benzene and carbon tetrachloride the variation fro m the reported val ue i:, by about 0.13 and 0.10 respect ively. In the re malfl ing liquids the ra t i o.~ are not readily avai lable for a co mpansoll.

Jt is observed from the spectra in Figs . 5 and 6 fo r CCI4, methyl butane, amyl acetate and methanol that the background accounts for an appreciable part of the tota l intensity signifyi ng a new mode as predicted 17

. Such a background has also been observed in CCl 4 wi th consid­erabl e asy mmetry in the Brillouin component sc. Also, it has been suggested that the prominence in the back­

ground depends on the relaxation time 'T arisin g out of the exchange of energy between the vibrational and translational modes . Spectral fea tures of these liquids suggest a closer look into the spectra and a detailed spectral analysis fo r an understanding of the relaxation mechani sms.

The Briliouin spectra of H20 and hydrogen peroxide H}O} both show a sharp Rayleigh line and a Brillou in shift of 0.20 cm- I indicating that H20 } is deco mposing rapidl y in to H20 and oxygen. The ca lculated intensity

ratios for 'Yare not in corres pondence with the other liquids of this study. 1n H}O} spectra a small shoulder at 0.065 cm- I embedded in the Rayleigh resembles similar to that observed in a CVO diamond film ll for a surface phonon mode. This is specific of H20 } due to the release of oxygen during its decompOSItion . meared Brillouin doublets have been observed in the spectra of methyl butane, propanol and methanol a sort of splittlflg III the central Rayleigh line. As the width of the Rayle igh line

(L1W DC 111 ) is inversely proportional to the rela xation time, a detailed anal ysis of the spectr .. d features need specia l attent ion. For hydrous quartz, the Brilloui n shift corresponds to longitudinal (LA) arid transverse(T A) acoustic ve loc ities which are fo und to be 5655 \11/S and 3535 m/s respect ively (Table I). These values are l es~

than those reported for a standard single crystal quartz and the differences can be attributed to the incorporatIon of hydrous component and i mpu ritie~ into the quartz sa mples studied . In the ca~e of natural gy psum the observed LA, TA velocities are 5 138 m/s and 3555 m/" respectively. The val ues shown in Table I for compari-

k . . 'II

son are on an evaporate roc con tcllnlllg gypsum- as ~ I

major mineral constituent and al so the measurements were at ultrasonic frequencies, hence the disparity in the ve loc ity values .

5 Conclusions A unique spectrometer has been desc ribed and used,

that can perform Raman , Brillouin and Rayle igh scatter­ing experiments in liquids and so li ds. The spectrometer cal ibrated with mercury I ines has been standa rd izcd by detect ing th e ch lorin e isotopes (C I ~ ·\' .Ch \'

342 INDIAN] PURE & APPL PHYS. VOL 38, MAY 2000

Tahle I - M easured Bri ll ouin s hift ~ (L'.WR) and intensity ratio (lR/2 / n ) fo r liquids and Brill ou in s hift~ of LA and T A in so lids

Material Specific gra vity

p

Carhon tetrachloride 0592

Amyl aeelate O.X66

M eth yl hutane O.61 f:

Propanol 07X:1

Benzene (} . X7~i

WaleI' 1.000

Hydrogen peroxide

Elhanol 07Xl)

Methanol () 700

NaturJI quart z 2.70()

aturJ I gypsum 1.:nO

"O'Connor ,Jnd SchlupI' ( 1064) "Parthasarathy and Bakshi ( 105:1) cpopp and Kern ( 19l)3 )

Refractive index 1/

1.4630

1.401 2

1.3959

1.4251

1.50 I I

1.3330

1.4 140

1.36 14

1.3286

1.5440

1.5230

(Ca lculated rrom ve locit y plot:, of Gypsum evapurate rucks )

CI17 1) 17· . ,Cb ' Cl 2 ' ) III the VI Raman mode of CC14.The

Brillouin shifts and integrated intensities in liquids and

solids have been used to calculate the acoustic velocities

(LA) in liquids, and LA and TA in hydrous mineral s.

The Landau and Placzek intensity rati os (I R/2/n) showed

a major di sparity in their y values (y > 2.0) for H20 2 and

H20 from other liquids of the present study. Spectral

featu res in most o r the liquids of the present study

showed that a considerable part of the total intensity

occurred as background under the Rayleigh and Bril­

louin components, suggesting the. poss ibility of a new

mode other than the thermal (Raylei gh) and the phonon

(B rillouin) modes. A spec ific feature in H20 2 spectra is

that TwO Brillouin shifrs. one at 0.20 and other at 0.065

cm- I (probably a surface Rayleigh mode) have been

observed during the rapid decomposition of H20 2 in to

H20 and O2. Further anal yses on These spectra are in

progress .

Brill ouin Acoustic veloc i ty Landau-Placzek shift - I

ra l io ill S - I cm 1({121H

Ohserved Kn(lwll

0. 120 003 035" O. '5 (0.72")

0. 150 11 72 1168 O.4X

0.11 2 875 0.66

o III 1004 9R5 (1.l)6

0.206 1504 1495" 0.0:1 m:·n")

(J.2(J() 163H 140X > 1.00

(J.200 1543 > 2.00 0.065

0. 145 1162 11 80" 0.61

0.141 1163 1207 068

0.80 (LA ) 5655 5840 0.50 (TA ) 3535 36XO

0.72 (LA ) 513X - 5000c

040 (T A) 3555 _ 2:;OOc

Acknowledgments The authors thank Dr H K Gupta, Director, National

Geophysical Research Institute, Hyderabad 500 O~, for hi s keen interest, encouragement and permi ss ion to pub­li sh thi s work .

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