DSpace at VNU: Design and construction of a laser raman spectrometer to study hydrocarbon extracts from petroleum of Vietnam

VNU. JOURNAL OF SCIENCE. Mathematics - Physics, T.xx, N03AP, 2004

D E S IG N AND C O N STR U C TIO N O F A L A S E R RAMAN
S P E C T R O M E T E R TO STU D Y H YD R O C A R B O N E X T R A C T S FRO M
P E T R O L E U M O F V IE T N A M
P h a m V a n B e n , N g u y e n T h e B in h , N g u y e n H u y B in h

D e p a rtm en t o f P hysics, C ollege o f Science, V N U
A b s tr a c t. W e stu died to d e sign a n d c o n s tru c t a la s e r R a m a n s p e c tro m e te r u sin g
an Argo n la s e r and a do u b le g ra tin g m on o c h ro m a to r G D M -1 0 0 0 . T h e effic ie n c y
o f th e la s e r R am an sc a tte rin g d e te c tio n s y s te m w a s e s tim a te d b y th e o b ta in ed
R am an s p e ctra o f s o m e s ta n d a rd s o lu tio n su c h a s C C I4, C 6H 6 a n d s om e
hyd ro ca rb o n e xtra cts fro m p e trole um o f V ie tn a m . T h is re s u lt is an im p o rta n t ste p
to s tu d y R am an s pe c tra o f p e tro le u m e x tra c ts in V ie tn a m a s w e ll a s R am an
spe ctra o f p h o to -e le c tro n ic m ate ria ls.

1.

I n t r o d u c tio n
L a s e r R a m a n spectroscopy h as becom e a n e ffective m ethod to s tu d y the com position

an d c on stru ctio n o f m ate rials, e sp e cia lly to a n a ly s e h id ro c a rc b o n e x tra cts from petroleum
and opto-electronic m aterials.. U s in g an A rg o n la s e r a n d a dou b le g ra ttin g m onochrom ator
G D M - 1000 we h ave

d esign ed an d

con stru cte d

a

La se r

Ram an

spectrom e te r in

our

laboratory. B y t h is system we o btain ed the R a m a n spectra o f som e s ta n d a rd so lu tio n such
as C 6H u, CC14... an d some h yd ro carb o ns e xtracted from p e tro leu m o f V ie tn a m .
2.

E x p e r im e n ta l s e tu p
T h e b a n d in te n s it ie s in R a m a n s p e c tru m m ay ra n g e fro m

1 0 2 to 10'6 % o f the

e x c ita tio n la s e r beam in te n s it y on th e s a m ple . T h e re fo re , p o w e rfu l e x c ita tio n sources
and

s e n s itiv e

d e te ctio n sys te m s a re

n e c e ss a ry

to o b t a in

a

Ram an

s p ectru m . T h e

s ch e m a tic d ia g ra m o f the b a s ic c o m p o n e n t o f th e la s e r R a m a n s p e c tro m e te r syste m w a s
sh o w n in the F i g . l . T h e e x c ita tio n so u rce is a n A rg o n la s e r w h ic h can g iv e p o w e r o f
172m W a t 4 8 8 ,ln m w a v e le n g th a n d 60 m W a t 476,5 n m w a v e le n g th . T h e la s e r b eam is
fo rcused on th e liq u id - s a m p le c e ll b y th e le n s o , (f|=7,7 cm ) a n d th e s c a t te rin g lig h t is
fo rcu sed o n th e m o n o ch ro m a to r e n tra n c e s lit h y th e le n s

0 2.

M o u n t in g tw o p la n e m irro rs G , a n d G 2on tw o s id e s o f th e s a m p le c e ll in cre a s e the
in te n s it y o f th e sca tte re d r a d ia t io n . B y th is w a y, th e la s e r b e a m is re fle c te d b a c k in to
th e s a m p le s ev era l tim es. T h e con cave m ir r o r G a ( f 3 =16 cm , Ộ = 10,5 cm) b r in g s b ack
o nto th e m o n o ch ro m a to r s l i t the r a d ia t io n

s ca tte re d b y th e s a m p le in

th e reverse

d ire ctio n , T h e m a in fu n c tio n o f th e o p t ic a l syste m is to se c u re o p t im a l c o n d itio n s fo r
s a m p le

illu m in a t io n

and

to

fo cu s

th e

s c a tte re d

r a d ia t io n

on

th e

m o n o ch ro m a to r

e n tra n ce s lit. T h e R a m a n sp e c tra is re co rd e re d b y a d o u b le g r a t tin g m o n o ch ro m a to r
G D M -1 0 0 0

and

a

p h o t o m u lt ip lie r tu b e

M I2 FC 5 1 .

T h is

s p e c tr u m

re co rd e r

system

o pe rates in th e ra n g e o f 2850 A 0 + 66 5 0 A 0 (23810 c m '1 -r 22727 cm ■') w it h
d is p e rs io n o f 3 A 0/mm.

11

the


PhamVanBen,NguyenTheBinh,NguyenHuyBinh

12

A T

F ig 1: The optical system scheme for sample excitation

3.

E x p e r im e n t a l r e s u lt s a n d d is c u s s io n
T o e x a m in e th e c a p a c ity a n d q u a lit y o f the R a m a n s p e c tro m e te r system w e fir s t

record ed the R a m a n s p ectra o f C C lj, C f,H 6. T h e n , w e re co rd e d R a m a n s p ectra o f some
h yd ro carb o n e x tra cts fro m p e tro le u m o f V ie tn a m . T h e se sa m p le s h a v e d iffe re n t b o ilin g tem p eratu res: 110° c

*

115° c fo r th e 5B110 s am ple an d 11 5 °c

■¥

120° c fo r the 5B115

sam ple. In the case o f C C lj, C 6H 6 w e recorded both R a m a n S to ke s a n d R a m a n an tiS tokes s p ectra (as sh o w n in F ig .2). T h is re su lt in d ic a te d th e h ig h e ffic e n c y o f th e la s e r
R a m a n s c a tte rin g d e te ctio n system . U s in g th is la s e r R a m a n s c a tte rin g d e te ction system
w e s tu d ie d to o b ta in s p ectra o f som e h yd rocarb on e x tra cts fro m p e tro le u m o f V ie tn a m ,
T h e sp ectra o f tw o sa m p le s o f V ie tn a m p e tro leu m e x tra cts w e re s h o w n in F ig .3

W e noted th a t in th e s p ectra o f both p e tro leu m sam ple s, th e re is a double lin e
w it h stro n g in te n s it y in th e re g io n o f 2840 cm '1 -r 2930 cm '1 a n d a lin e o f w e ak er
in te n s ity a t 1444 cm '1 fo r th e case o f 5B110 s a m p le an d a t 1454 cm '1 fo r the case o f
5B 1 15 s a m p le an d som e lin e s o f ve ry w e a k e r in te n s ity in th e re g io n o f wave n um b e r
s h o rte r th a n 1444 c m '1.


D e s ig n a n d c o n s tr u c tio n o f a la s e r ra m a n ...

13

B a s in g on th e c h a ra c t e r is t ic o f b o ilin g -te m p e ra tu re , in te n s it y a n d fre q u e n cy s h ift
in R a m a n s p e c tra o f th e tw o sa m p le s o f V ie tn a m

p e tro leu m e x tra cts [2,3] w e cou ld

c o n c lu d e t h a t th e tw o s a m p le s con s is ted o f 2 -M e ty l p e ntane, X y c lo p e ntane, O ctane,
E ty x ic lo h e x a n , N o n a n . p -X y le n a n d 2,

6

D im e ty l h eptanes... A l l the se com p ou n d s b elong

to p a ra ffin , n a p h th a le n e a n d a ro m a tic h yd ro carb o n s fa m ily [5]. T h is re s u lt w a s in good
a g re e m e n t w it h s e v e ra l o th e r d ocu m en ts re p orte d on p e tro leu m o f V ie tn a m .

Fig.3: The Raman spectra o f petroleum extract samples excited by 476,5nm wavelength
of Argon laser : a - for sample 5B110 , b - for sample 5B115

4.

C o n c lu s io n s
A

la s e r R am a n sp ectrom etry system w ith an A rg on la s e r an d a d ouble g rating

m onochrom ator G D M -1 0 0 0 h a s been developed a t o u r laboratory.

Several studies were

carried o u t to design optical system fo r o ptim al sam ple excitation. T h e o btain ed R am an
spectra sho w ed th a t th is la s e r R a m a n spectrom etry system cou ld give h igh se n s itiv ity and
resolution. It is s u ita b le not o n ly to analyze hydrocarbon com pounds o f petroleum b ut also
to study sem icon d uctor m ate rial structure.
A c k n o w le d g e m e n t s :

T h i s w o r k w a s s u p p o rte d by the S c ie n tific R e s e a rch P ro g ra m

o fV N U

References
1.

H B a ra tis k a , A .L a b u d z in s k a , J.T e rp in s k i,

A Laser Ram an Spectrom etry

- E llis Howood

J.W ile y & Sons 1987.
2.

F.R

D ollish,W ,G . Fateley,

Characteristic R am an Frequencies o f Organic compounds,

Wil3ey-Interscience. N e w Y o r k 1974.
3.

B e rn h a rd S chrader,

Infrared an d Ram an Spectroscopy

W einh em -N ew Y o r k - 1994.