cac phuong phap pho raman (1)

7/30/2019 Cac Phuong Phap Pho Raman (1)

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3.1.QUANG PH RAMAN PHI TUYN: (135)1. Hiu ng Raman tinh t (HPS)2. Hiu ng Raman kch thch (SRS)3. Hiu ng Raman o ngc (IRS)4. Ph Raman i Stokes kt hp (CARS)5. Ph Raman m quang (PARS)

Nh bit, vect momen lng cc cm ng P c tnh theo cng thc:

...6

1

2

1 32+++=

EEEP (1.1)

Vi E l in trng ca chm laser, l phn cc, v l phn cc th nht v thhai. i vi ph Raman thng vi laser CW (E = 104 V/cm) th s ng gp ca 2 thnh phn v vo ln ca P l khng ng k v >> >> .

Raman tinh t Raman kch thchHnh 1-1 S

dch chuyn linquan n mi loi

quang ph Ramanphi tuyn.

ng gpca chng tr nnng k khi muc chiu x vinhng xung lasercc mnh (~ 109

V/cm) c to bilaser ruby Q

Switched hoclaser Nd YAG(cng sut cc i10 100 MW).

Nhng xung khngl ny dn n hintng quang phmi, v d nh hiung Raman tinh t,hiu ng Raman

kch thch, hiu ngRaman o ngc(IRS), tn x iStokes kt hp(CARS), phRaman m quang(PARS).

3.1.1 Hiu ngRaman tinh t:

Khi muc chiu sng

bng mt xung khng l vi tn s , bc x b tn x tn s 2 (tn x Rayleigh tinh t) v 2 m


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(tn x Raman tinh t Stokes v i Stokes kt hp), vi m l tn s ca mt dao ng chun ca phnt. Hiu ng Raman tinh t l qu trnh 3 photon lin quan n 2 trng thi o ca tn x.Tn x Ramanc gy ra bi 2 photon ti ca chm laser. Theo thc t, hin tng ny kh quan st v ch c 10 -12

bc x bin i sang 2 m v v cng bc x c th tng ch n mt gii hn cho php xcnh. Nu tng cng bc x vt qu gii hn cho php th hiu ng Raman kch thch s tr thnhch yu hay tri hn hiu ng Raman tinh t. Ph Raman tinh t c mt s thun li so vi ph Ramanthng v mt s khc nhau trong cc quy tc lc la. Chng c quyt nh bi tch ca cc thnh

phn ma trn ca 3 momen lng cc lin quan n 4 mc c trnh by trong hnh 1-1. Nh ta bit, mt dao ng l hot ng Raman nu t nht mt trong cc thnh phn ca tens phn cc thayi trong sut qu trnh dao ng. Tng t, mt dao ng l hot ng Raman tinh t nu t nht mttrong cc thnh phn ca tens phn cc tinh t thay i trong sut qu trnh dao ng.

Hnh 1-2 S mc ca tn x ca tnx Rayleigh tinh t vtn x Raman tinh t.

Bng 1-1 sosnh cc tnh cht ixng ca 2 thnh phnca nhm im D6h(benzene). Nhiu daong khng phi l hot

ng hng ngoi (IR) hoc hot ng Raman tr thnh hot ng Raman tinh t (B1u, B2u, E2u). Bng 1-

1 cng cho thy rng mt s dao ng l hot ng Raman khng l hot ng Raman tinh t (E 1g, E2g),trong khi tt c cc dao ng l hot ng IR th s l hot ng Raman tinh t (A2u, E1u). Cc hiu ngtng t cng c quan st trong cc nhm im khc. Ngoi ra, hiu ng Raman tinh t cn cho

php quan st cc mode tnh (silent) m ph IR hoc ph Raman tuyn tnh khng quan st c. PhRaman tinh t quan st i vi cht kh, lng, rn.

Bng 1-1 Quy tc lcla i vi ph IR(hng ngoi), Ramanv Raman tinh t caBenzene (D6h).

I.2 Ph Raman kchthch:Trong tn x Raman

thng, bc x laser chiu vo mu to rahiu ng Raman t

pht ( - m ) nhngcng th rt yu.

Nu in trng calaser vt qu 109

V/cm, tn x Ramantinh t s tr thnh tn x Raman kch thch m hin tng ny sinh ra mt chm kt hp c cng mnh ti tn s Stokes ( - m ). Hnh 1-3 trnh by mt thit b thng thng c s dng cho vicquan st hiu ng Raman kch thch. Bc x laser khng l () c hi t vo mu (benzene), v nh


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sng b tn x s c quan st dc theo hng ca chm tia ti. Nu mt phim mu nhy c ttheo hng (phng) vung gc vi chm tia ti, ta s quan st c nhng vng trn mu ng tm

c ch ra trong hnh1-3. Mt iu th v lmode chun ( m ) mnhnht trong mt phRaman thng th ctng cng mt cchcc mnh trong hiung Raman kch thch.Trong benzene, rngvng cm Eg l 992 cm-1. Thc t, khong 50%chm nh sng ti cchuyn i sang vchStokes u tin ( - m ).V vch ny c cng

mnh nn n hotng nh mt ngun kch thch vch Stokesth hai, ( - m ) - m =

-2 m v vch ny li hot ng nh mt ngun cho vch Stokes th ba, th t, v.v Do , nhngvng mu ng tm c quan st tng ng vi cc tn s , - m , -2 m , -3 m , -4 m , v.v

Nn ch rng, tn s 2 m quan st c chnh xc gp 2 ln so vi tn s m v khng bng ho mba u tin ca tn s m (s iu chnh tnh khng iu ha). Hiu sut chuyn i cao ca hiu ngRaman kch thch c th c s dng sinh ra nhiu vch laser vi nhiu tn s khc nhau.

I.3 Hiu ng Raman o ngc:Gi s rng mt hp cht c mt dao ng l hot ng Raman c tn s m . Nu n c chiusng bi mt my laser pht tn s mt cch ng thi vi vng tn s lin tc t + 3500 cm-1.

Ngi ta quan st c mt s hp th ti tn s + m trong vng tn s lin tc v s pht x ti tns . Nng lng hp th h( + m ) c s dng cho s kch thch (h m ) v pht x nng lng d(h). Dch chuyn ln c gi l hiu ng Raman o ngc v dch chuyn i Stokes trong phRaman tuyn tnh xy ra i xung. V ph Raman o ngc c th thu c trong thi gian sng caxung nn n c th c dng cc loi c thi gian sng ngn. Nn ch rng, thi gian sng caxung ca vng tn s lin tc phi bng vi xung khng l . Do , hiu ng Raman o ngc

c quan st ch trong mt vi hp cht v kh sn xut mt xung lin tc trong vng tn s mongmun.I.4 Ph Raman i Stokes kt hp (CARS):

Khi mu c chiu x bi 2 chm laser nng lng cao vi tn s 1 v 2 (1 > 2) theo mtphng cng tuyn (hnh 1.4), hai chm tng tc vi nhau mt cch kt hp to nh sng tn x mnhti tn s 21 2. Nu 2 c iu chnh n mt iu kin cng hng: 2 = 1 m vi m l mt tns ca mode hot ng Raman ca mu, sau mt nh sng c cng mnh ti tn s 21 2 =21 (1 m) = 1 + m c pht x (hnh 1.4). Qu trnh nhiu photon ny c gi l ph Ramani Stokes kt hp (CARS). CARS c nhng thun li sau y:

a. V nh sng CARS (1 + m) l kt hp v c pht ra theo mt phng vi mt gc khi

nh nn n c pht hin mt cch d dng v hiu qu m khng cn mt my n sc. Thm vo, s nhiu x hunh quang c th trnh c nh tnh cht nh hng ny.


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b. Tn s CARS (1 + m) cao hn 1 hoc 2. Do , n nm pha bn vch i Stokes ca tns bm (1) trong khi hunh quang nm bn pha vch Stokes, do iu kin ny cng phn bit vihunh quang.

c. V tn hiu CARS rt mnh nn cc hp cht kh c nng thp cng c th c pht hin.d. Cc quy tc lc la khng c p dng trong ph Raman thng li c th p dng trong

CARS. Tt c cc mode hot ng Raman u l hot ng CARS. Ngoi ra, nhiu dao ng khngphi l hot ng Raman, trong mt vi trng hp khng phi l hot ng IR tr thnh hot ngtrong CARS.

Thit b CARS c gi thnh cao.Hnh 1.4 Thit b banu cho vic olng pht x iStokes l s dnglaser Nd: YAG (tns kp) bm lasermu c tn s kp. Ll thu knh c tiuc ngn (3 4 cm). I

l mng mt lc 2chm tia kch thch. F

l b lc giao thoa di rng. D l detect (thng l mt pin diode). M l my n sc (thng khngcn thit). Cc thnh phn khng trnh by trong hnh v l hp mch tch hp PAR 160, my ghi, vlaser mu ghi ph.I.5 Ph Raman m quang (PARS):

Nguyn l ca PARS tng t vi CARS. Khi 2 chm laser, chm bm (p), chm Stokes (s)i vo mu kh c cha trong mt (hnh 1.5), 2 chm ny tng tc vi nhau khi c iu kin cnghng (p s = m, m mt tn s ca mt mode hot ng Raman. Kt qu l chm Stokes ckhuch i v s tt dn ca chm bm. Mi photon Stokes c sinh ra mang phn t ln trng thi

kch thch v s kh trng thi kch thch ca cc phn t bng va chm lm tng nng lng chuynng tinh tin ca chng. S thay i trong nng lng chuyn ng tnh tin lm thay i p sut camu bn trong . S thay i p sut ny c th c pht hin bng mt micro. Vic s dng dng c

pht hin m l c nht trong cc k thut quang ph hc. Bng vic qut s (s dng mt laser mu),s thay i p sut c o v chuyn sang mt ph. V d, hnh 1.5 ph Raman quay ca CO 2 c

c bi PARS. Svng mt ca dyRayleigh mnh tothun li cho PARSc th nghin cudch chuyn quaynng lng thp cahp cht kh.

Hnh 1.5 Biu th hin qu trnhPARS. (a) S mcnng lng n ginminh ha s tngtc Raman xy ratrong PARS. Ccthnh phn c bnca thit b PARStrong thc nghim.Chm bm b tt dn


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v chm Stokes c khuch i bi qu trnh Raman kch thch m n din ra khi cc chm bm phnhau trong cha mu cht kh. Mi photon c to bi qu trnh Raman th mt phn t chuyn ttrng thi thp ln trng thi cao hn. S hi phc bng va chm ca cc phn t b kch thch lm snxut mt s thay i p sut v c pht hin bng mt mirco.

Hnh 1.6 PhRaman quay quang m

ca CO2 ti p sut 80KPa (600 Torr). Khongcch gia 2 vch quay lkhong 3.1 cm-1. Cngsut ca chm bm vchm Stokes tng ngl 3.3 MW v 120 KW.

3.2.PHNG PHP QUANG PH RAMAN PHN GII THI GIAN (142)1. i tng phn tch2. Nguyn l o

3. Thit b o4. ng dng

1. i tng phn tchCc mu trng thi chuyn tip c thi gian sng ngn. Vd:Phn ng ha hc: A + B C + DHai bc:A + B X*X* C + D2. Nguyn l o

u tin, cc phn t c kch thch t S0 (trng thi n c bn) n S1 (trng thi n kchthch) bng cch bm laser vi tn s v0. Cc phn t kch thch n S1 xung mc T1 (mc 3) khng

pht . Sau , rng xung bm ngn hn thi gian sng ca T1 (t mili n micro giy), s kch thchn trng thi S1bi 1 laser bm gia tng dn s trn mc T1, ni c th n quan st c phRaman ca phn ti trng thi T1 vi 1 laser u d (v1). Nu v1 c chn gp iu kin cnghng nh hnh 3.6, c th c cng hng c ni n 1.15. Do , Quang ph Raman phn giithi gian (TR3) l tng quan st ph ca trng thi phn t b kch thch. 1 vi hp cht c v1 gnvi v0. Trong vi trng hp cn thit quan st ph TR3 s dng 1 laser n.

Xung laser nh Nd: YAG v laser excimer thng c s dng bm d th nghim va mi cp. Vi c tnh ca cc laser ny c ghi bng 3-2. Mc d laser c bn ca Nd:YAG l 1064nm, tn s ny c th c nhn ln bng cch s dng tinh th khng phi tuyn, vd: KDP quan stcc ha ba th 2 (532), th 3 (355), th 4 (266). Hn na, phm vi m rng bc x xung tia UV nhnthy c th c pht ra t nhng ha ba (ha m) bng cch bm 1 laser mu hoc s dng 1 b dchchuyn Raman.


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2. Thit b o


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H thng o phHnh 3.7 cho thy s sp xp quan st ph TR3 ca trng thi kch thch carotenoid. 1 trong nhngthc nghim, Laser II (355 nm) c dng sinh ra trng thi phn t T1 thng qua s kch thch ca1 cht lm nhy (anthracence) v nng lng theo sau chuyn n carotennoics. Laser I (532 hoc 555-610 nm laser mu) c dng quan st ph RR ca vch ba carotenoids. Thi gian tr thch hpgia s bm v xung u do c xc nh bng thi gian yu cu tch ly tng dn s trngthi T1. th nghim ny, thi gian tr di (~micro giy) s cn thit 2 laser ring bit c dng

cho s kch thch v d tm. Thi gian tr nhiu c th c thc hin bi in t bng cch khi ngnhanh 2 laser lin tip. Nu 1 thi gian tr tng i ngn c yu cu, v 1 ng truyn quang hctr, nh hnh 3.7, c th c thc hin. Trong vi trng hp, do 1 s tr l khng cn thit k t khitrng thi kch thch ca vng quan tm c thc hin trong phm vi rng 1 xung (10 ns). nhchnh ca xung c s dng cho vic bm v s ngng li ca u d. .145


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3.3 QUANG PH RAMAN TCH NN (147)K THUT MINguyn l

Cc mu MI sau c th c thm d bi bt k k thut quang ph c sn nh: Quang ph hng ngoi,Raman Ph hp th tia UV-kh kin Ph hunh quang cm ng laser Cng hng spin in t Ph Mssbauer

Trong phng php ny, mu th kh v cht nn kh tr,vd: Ar hay Kr c trn ln vi nhau v lngng trn 1 ca s mu trong sut IR (Vd: tinh th ..) c lm lnh n 10-20K bng my iu lnh.

Khi trn ln vi t l 1/500 hay cao hn, cc pt mu c tch ln nhau hon ton trong cht nn khng lnh. Do , ph MI ging nh cc pha kh ; khng c s tng tc gia cc phn t bn trongtn ti v khng c mode ca mng c quan st (mc d s tng tc yu qua li gia cht ha tanv kh tr c ch ). Hn na, ph MI n gin hn ph ca pha kh v ch 1 vi hoc khng c sdch chuyn quay c quan st thy, kt qu ca s gii hn b tr ca s quay phn t trong th nn. nt ca dy c quan st dn n phn tch c cc dy c nh v. K thut MI cng cho

php mu rn c th bc hi khng cn phn tch (phn ly).Quang ph Raman kh ng dng i vi cht nn c nhit thp hn quang ph hng ngoi v nhngl do sau:(1) Khi tn hiu Raman vn yu, lin quan n nng ca mu hoc b rng khe c thc hin.

Trc gy ra s hnh thnh ca cc dng nh trng v polymer, trong khi sau dn n mt nnglng phn tch ca my phn tch.


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(2) Nu tng nng lng laser quan st tn hiu Raman mnh hn, nhit s nng ln v nhit ccb gy bi chm laser, v iu ny lm thc y s khuch tn nh sng ca cc phn t trong dungdch cht nn.-> (1) v (2) c th b ph v nu ph Raman c quan st di iu kin cng hng.(3) Cht lng ca ph Raman quan st ph thuc vo tnh cht ca cht nn c chun b.; cc chtnn sch, r rng cho kt qu tt hn cc cht nn u m. Tuy nhin, vic chun b ban u i himt nhiu thi gian.(4) Cht nn hoc tp cht du t s bm khuch tn nh sng c th gy ra hin tng hunh quang.

Bt chp nhng vn ny, quang ph Raman tch nn vn thun li hn bn sao ph hng ngoi.

Thit b:Th nghim thit lp quang ph Raman nn v c bn ging nh quang ph hng ngoi nn. S khc

bit chnh nm hnh dng quang hc. Hnh dng tn x ngc phi c thc hin trong quang phRaman khi kh nn v mu bc hi c lng ng trn 1 b mt kim loi lnh (Cu, Al). Hnh 3.10 chothy s sp xp. K thut sy nh c thc hin ha hi mu rn, v 1 thu knh hnh tr cdng cho ra 1 ng hi t m t trn cht nn hiu ng nhit cc b do chm laser c cctiu ha.

Trc tin, cc ca s mu c lm lnh n 10 K (4 K cho cht nn neon) v c t i

din vi nhng trc tia ca quang ph k, ni mt ph nn ca b mt trng c ghi. Sau , ca s c quay i din vi cc cng lng ng mu. Hi PAH c to ra bng cch

thng hoa ca mt mu PAH rn c t trong mt ng nghim pyrex .Cc dng kh tr i voh thng thng qua mt cng lin k. Hai lung hi lin hi p v ng bng trn b mt ca cas lnh. Sau khi mt lng ph hp ca mu c lng ng, lp nn c quay tr v v tru tin v ph ca n c ghi li v c truyn n quang ph nn

i vi cc nghin cu quang ph ca cc loi c to ra bi quang phn bng tia t ngoi,cclp nn sau c th c quay i din vi mt cng th ba c gn kt vi mt n dnghidro pht ra vi sng

ng dng K thut ny c th gip bo qun mu trong thi gian di. Thch hp nghin cu cc loi ion v gc t do hot ng mnh kh c th to ra v duy tr

pha kh. K thut ny c th p dng vi cht rn min l n c th c ha hi m khng b phn hy. Ph MI c s dng rng ri cho cc nghin cu trong ha hc v vt l sau y:

Cu to (conformations ) trong phn t Tng tc yu gia cc phn t Cc yu t ha hc v cc phn ng nhit cao, ng dng trong ngnh ht nhn v nghincu khng gian. Cc c ch phn ng ng dng trong phn tch


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PH M.INguyn l Ph Raman MI phi c quan st di tnh trng cng hng. Trong thit lp th nghim o ph MI Raman phi b tr hnh hc cho tn x ngc v mu MI

c gi nhit rt thp.Thit b /150ng dng ng dng trong lnh vc ha v c, nghin cu cc loi ion, gc t do...vd:Nghin cu ph Raman ca sn phm phn ng gia kim loi kim vi nguyn t halogen trn

nn kh tr (Andrews v cc cng s)

Ph Raman tch nnPhng php tch nn:

Nguyn l: Trong phng php ny, mu ( pha kh) v cht nn (thng l kh tr) c trn ln v lngng trn mt b mt c lm lnh ti mt nhit rt thp (khong 10K). Cho n khi t l gia cc phnt mu v cht nn l rt nh (vi chc n vi trm phn trm) th cc phn t mu s b cch ly, c lp vinhau trong cht nn. Sau khi to thnh cc mu tch nn (MI),cc mu MI sau c th c thm d bi

bt k k thut quang ph c sn nh:

Quang ph hng ngoi,Raman Ph hp th tia UV-kh kin Ph hunh quang cm ng laser Cng hng spin in t Ph Mssbauer

Phng php tng hp cc phn t mu MI:C hai phng php chnh tng hp cc phn t mu MI: S to thnh bn ngoi v Tng hp bn trongi vi s to thnh bn ngoi, Cc phn t pha kh t cc hn hp, c lng ng vi mt lng d khnn, hoc Cc phn t pha kh c to bi cc phn ng ha hc, c lng ng vi lng d kh nni vi s tng hp bn trong, mu c to ra bi cc phn ng ha hc tc thi trong cht nn, hoc do squang phn ca cc tin cht tch nn.

Ty theo yu cu nghin cu m ta c th s dng mt hoc kt hp cc phng php ny vi nhau.Thc nghim:

Trc tin, cc ca s mu c lm lnh n 10 K (4 K cho chtnn neon) v c t i din vi nhng trc tia ca quang phk, ni mt ph nn ca b mt trng c ghi. Sau , ca sc quay i din vi cc cng lng ng mu. Hi PAHc to ra bng cch thng hoa ca mt mu PAH rn c ttrong mt ng nghim pyrex .Cc dng kh tr i vo h thngthng qua mt cng lin k. Hai lung hi lin hi p v ng bngtrn b mt ca ca s lnh. Sau khi mt lng ph hp camu c lng ng, lp nn c quay tr v v tr utin v ph ca n c ghi li v c truyn n quang ph nn.i vi cc nghin cu quang ph ca cc loi c to ra biquang phn bng tia t ngoi,cc lp nn sau c th cquay i din vi mt cng th ba c gn kt vi mtn dng hidro pht ra vi sng.

u im ca k thut: K thut ny c th gip bo qun mu trong thi gian di. Thch hp nghin cu cc loi ion v gc t do hot

ng mnh kh c th to ra v duy tr pha kh. K thut ny c th p dng vi cht rn min l n c th c ha hi m khng b phn hy.

ng dng k thut tch nn:


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Ph MI c s dng rng ri cho cc nghin cu trong ha hc v vt l sau: Cu to (conformations ) trong phn t Tng tc yu gia cc phn t Cc yu t ha hc v cc phn ng nhit cao, ng dng trong ngnh ht nhn v nghin cukhng gian. Cc c ch phn ng ng dng trong phn tch

Ph Raman tch nn:L Ph Raman ca mu MI* Yu cu: Ph Raman MI phi c quan st di tnh trng cng hng. Trong thit lp th nghim o ph MI Raman phi b tr hnh hc cho tn x ngc v mu MI c gi

nhit rt thp.* Thit b:S hot ng ca thit b o ph

Raman cng hng tch nn: 1, lp bcngoi bng thy tinh; 2, l nhm; 3,hthng lm lnh; 4, ng dn kh; 5, mn

bng thp; 6,u nhn c lm lnh;

7, tm bo v khi s pht x; 8,lp baongoi bng thy tinh chu nhit; 9,thanhch pht ra tia la; 10, ng mao dn chamu; 11, gng nh; 12,thu knh hnhtr; 13, thu knh hi t y, h cc gng, thu knh11, 12, 13c b tr theo kiu hnh hc cho tn xngc. u tin, khi cha c mu, ph bmt trng c ghi. Sau , mn s 5 cquay sao cho chn ngay ng truynquang u d 6 ti my quang ph. Mu

cha trong ng s 10 c ha hi nh thit b s 9, sau hi ny c phun ti u d lnh 6. Cng lc ,kh nn cng c phun vo qua ng s 4. Hai kh ny lin hp v ng bng trn u s 6. Sau mn 5c quay i, mu lc ny s nm ngay trn ng truyn quang hc ti my quang ph, ph Raman ca n sc ghi li v cho ta thng tin cn thit.

*ng dng:Ging vi ng dng ca ph MI, c bit l dng nhiu trong lnh vc ha v c, nghin cu cc loi ion,gc t do.

3.4. QUANG PH RAMAN P SUT CAO (153)Nguyn lK thut p sut gm 1 thit b p sut (DAC) c th truyn p sut n mu. Nu phng php quang

ph c chn cho mc ch chn on, th y l 1 nhu cu tt yu s dng nhng khe ca trnthit b p sut, n phi cng v truyn nh sng bc x bc sng ring bit ca quang ph in t.Ca s c chn cho hng ngoi v Raman nghin cu l dng kim cng IIa. N l cht liu cngnht v c th truyn c laser raman cn nghin cu. Thm vo , n l cht dnn nhit rt tt.Thit b p sut phi c lm chc chn v va vn vo trong bung ca mu trong my quang ph.S chun ha p sut l cn thit v iu ny c thc hin bng cch kt hp 1 tinh th nh ruby vimu cn nghin cu.

Thit bDng c Raman theo quy c l thch hp cho dng c o Raman p sut cao. Thit b o p sut cth l 1 bung pittng-xilanh hoc 1 DAC (diamond anvil cell: bung u o bng kim cng)


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Chi tit ca DAC u tin: A, B: Piston, C: vt kim loi cng c gn vo, D: bn kim loi nn , E:n by, G: inh vt, inh c, H: l xo iu chnh. p sut c p dng bng cch vn nm iu khin nn l xo. p sut c truyn qua n by v nn bn kim loi pha di y 2 pittng cc kimcng li vi nhau v nh hng n p sut.Bc x laser bc sng 632,8 v 476,5 nm c ngh, v bc x khong 514,5 v 488,0 nm c thgy ra vn pht hunh quang.S chun ha p sut c thc hin tt nht khi s dng t l Ruby. Ni chung iu ny c thchin khi dng 1 ming m kim loi gia 2 khe kim cng bao quanh mu trong 1 dung dch (Vd: du

Nujol hoc Teflon) c thm vo cho ra p sut thy tnh. K thut ny o p sut khc nhau giahunh quang Ruby R1 bc sng 692,8 nm, d dy R2 694,2 nm cng c dng. Hunh quangRuby c gy ra bng kch thch mu xanh ca laser Ar+ (488 nm) hay He-Cd (441,6 nm)

ng dng(a) S chuyn pha rn vi p sut

S chuyn pha trong th rnS thay i p sut trong hp cht phi tr th rnDu hiu ca s m kim loi ca hydrogen p sut (Mbar:Megabar)Th nghim vi nhng vt liu quan trong n vn v si khoa hc Earch

3.5. Raman tng cng b mt (SERS) (160)Nguyn l

Phng php SERSPhng php SERS ( Surface Enhanced Raman Spectroscopy) l phng phptng cng vch Raman bng plasmon b mt.Nguyn l

Khi sng in t truyn dc b mt mt tm kim loi vi tn s sng nh hn tn s plasma ca electron trongkim loi, tng tc ca sng v plasma electron ( mt trng thi m tt c cc electron chuyn ng nh mt ththng nht) lm sng in t c th thm nhp vo mi trng ( gn b mt) v nh x . Dng surface

plasmon c th tng cng in trng mt cch cc b, v th, khi a nguyn t cn o ph Raman vokhu vc in trng cao , tng tc gia nguyn t v trng in t s mnh hn, dn n ph Raman c

cng ln hn.S thit b o SERS (hnh 1 v hnh 2 u c)

Hnh 1: Tia laser nmtrong vng ph nhn

H.1


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l i lng c trng, c th dng phn bit nguyn t ny vi nguyn t khc. Chnh v th, tnh

ng dng ca ph Raman l rt ln.

Tuy nhin, so vi cc qu trnh tn x n hi ( nng lng ca photon khng i) th xc sut

xy ra tn x Raman l rt nh. quan st c vch Raman, ta phi: tng cng ca vch Raman

v tch vch Raman khi vch chnh.

Vic tch ph c th thc hin kh n gin bng mt knh lc, hay phc tp hn mt cht lphp bin i Fourier. H bin i Fourier l mt h ph bin trong ngnh quang hc v quang ph,

ngi ta dng mt h giao thoa k Michealson vi mt gng c th dch chuyn. dch chuyn ca

gng c th iu khin chnh xc nh h vn giao thoa ca mt laser c bc sng cho trc. Da

vo dch ca gng, ta c th c hm Fourier ca ngun sng cn nghin cu.

c c cng vch Raman ln, cch n gin nht l chiu chm sng ti vi cng

ln v d nh dng Laser chiu, nhng cch ny cng khng hiu qu lm.

Phng php SERS ( Surface Enhanced Raman Scattering), tng cng vch Raman bngplasmon b mt ( surface plasmon). Plasmon b mt l mt dng lng t ca trng in t trong mi

trng plasma c hng s in mi m, v d nh trong kim loi vi tn s sng in t nh hn tn s

plasma ca electron trong kim loi.

Khi sng in t truyn dc b mt mt tm kim loi vi tn s sng nh hn tn s plasma ca

electron trong kim loi, tng tc ca sng v plasma electron ( mt trng thi m tt c cc electron

chuyn ng nh mt th thng nht) lm sng in t c th thm nhp vo mi trng ( gn b mt)

v nh x . Dng surface plasmon c th tng cng in trng mt cch cc b, v th, khi

a nguyn t cn o ph Raman vo khu vc in trng cao , tng tc gia nguyn t v trng

in t s mnh hn, dn n ph Raman c cng ln hn.

Phng php SERS rt kh thc hin v ph thuc nhiu vo tnh cht b mt kim loi v tn s

plasma ca kim loi.

3.6. Raman in ha (165)Mc ch:+ Xc nh tnh cht v cu trc ca cc phn t+ Quan st cc qu trnh ng hc ca cc mu pht in trong cc mi trng thng gp: trong dung dch hatan, lp khuch tn in, b mt cc in cc. ngha:+ T l S/N (sign/noise) cao+ Quan st mt lng nh mu (10-3 10-5M) trong dung dch cht ha tan,1013 - 1014 nguyn t trong lpkhuch tn v 1012 1013 nguyn t trn b mt lp in cc

Khi nim:

Dung dich ha tan

Lp khuch tn in

B mt in cc


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+ Dung dch ha tan: Khi nghin cu mt cht vi nng t, ta cn phi ha tan vo mt dung dch (c hotng raman km). Do ta s thu c ph raman cn o ca cht cn o+ Lp khuch tn in: c to ra do lc tnh in v chuyn ng nhit ca cc in tch, ion ti vng trn vmt cc in cc.+ B mt cc in cc: l lp in tch b mt (m hoc dng). t cc phn t, nguyn t ln b mt cc incc, di nh hng ca in trng ti b mt s tng cng ph raman ln rt nhiu.Thit b:Hnh a minh ha mt ngun thng dng thu ph RR ca cc loi ht pht sinh in trong dung dch . Tialaser c hi t trn mt v tr c th c dch chuyn ra khi b mt in cc lm vic. S tp trung ca cc

ht c nghin cu c tch ly thng qua s pht in th c iu khin. Cc loi ht c to ra phi bntrong thi gian yu cu nhm ghi c ph ca n, do khng xy ra s nhiu lon do cc sn phm cphn ly. Nu cc ht pht sinh in ch bn mt nhit thp, ph RR ca n phi c o bng mt t boin phn nhit thp.

Auxiliary electrodeReference electrodeWorking Electrode


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Hnh b l thit b sandwich o ph RR ca cc loi ht pht sinh in trong lp khuch tn. Tia laser bphn x t in cc bch kim hot ng v nh sng phn x c o thng qua h hnh hc tn x ngc. Snhiu lon ph t dung dch c th trnh c bng cch chn mt h thch hp i vi kch thch RR.

in ha l tn gi mt lnh vc trong ha hc nghin cu v mi lin h gia cc qu trnh ha hcv dng in.Mt phn ng ha hc xy ra khi c dng in chy qua, hay qua phn ng ha hc c mt hiu inth, y l nhng qu trnh in ha.Cc phn ng in ha xy ra trong dung dch, ti b mt tip xc gia cc vt dn inPh in ha cung cp cc thng tin: dng in, in tch, th, tn s, thi gian,Mc ch+ Xc nh tnh cht v cu trc ca cc phn t+ Quan st cc qu trnh ng hc ca cc mu pht in trong cc mi trng thng gp: trong dungdch, lp khuch tn in, b mt cc in cc.ng dng+ Trong sn xut cc kim loi nh kali, nhm, ... hay cc halogen nh clo, flo, ... qua in phn

Auxiliary electrodeReference electrodeWorking ElectrodeSaturate Calomel Electrode


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+ Sn xut cc ngun in di ng nh pin, c quy, t bo nhin liu, ...+ Phn tch cc cht ha hc trong ha phn tch,+ K thut m inPhng php nghin cu+ ph hp thu in ttrong tia UV, vis, v NIR: electronic absorption spectroscopy in the UV.,vis., and

NIR+ ph hng ngoi: infrared (IR) spectroscopy+ cng hng spin in t : electron spin resonance (ESR) spectroscopy (odd electron: in t trng)

+ ph cng hng t tnh nuclear magnetic resonance (NMR) spectroscopy+ Trc khi ph: mass spectrometry (MS)Ph in ha Raman+ observe high S/N spectra for 10-3 - 10-5 M electrogenerated species in bulk solution+ observe 1013 to 1014 molecules, ions, etc., generated in the few micron thick diffusion layer of anelectrode+ observe 1012 to 1013 adsorbed molecules in a monolayer on an electrode surface

Mc ch:+ Xc nh cc mode dao ng RR trong trng thi nn ca cc phn t v s thay i cu trc

in t trong qu trnh trao i cc electron

+ S dng RRS xc nh trng thi kch thch ca cc ionQuang ph Raman in ha nghin cu cc loi pht in trn b mt in cc, trong lp in cckhuch tn v dung dch bng quang ph Raman. Do , tn x Raman tng cng b mt (SERS)

3.7 Knh hin vi Raman (172)Knh hin vi Raman c pht trin vo nhng thp nin 70. Vo nm 1975, Delhaye ch to h thng

o lng Raman cc nh u tin. Cng trong nm , Rossaco thit k my vi d Raman (microprobe) (lthit b ng dng tnh n nh v hi t chm ht mang in (e -, in) n mu). u tin l thit lp s ngdng ca Quang ph hc Raman vo php phn tch vi lng. K thut ny cho thy kh nng thu nhn tnhcht quang ph Raman cn phn tch vi phn gii khng gian l 1 m p dng cho mu trn 1 phm vi

picogram (10-12

gram).3.7.1. Nguyn lGii hn ch yu trong thit k ca my vi d Raman lin quan n hiu ng Raman m (feeble Raman

effect) v kch thc mu qu nh. Do rt cn thit ti u ha tn hiu Raman, v n c thc hin bngcch ch n s khuych i ng i quang hc pha trc (fore optical configuration). p ng hotng bng s v h thng my d cao.

1 khu s (numerical aperture) cao (NA) : thu nhn s tn sc nh sng trn 1 gc khi ln mbo nhiu tia Raman c tn sc t mu vt c nhn thy.

1 khe thu ln (aperture collector) : dng lm gim s tn x n hi v khng n hi ti mc tithiu t lp cht nn.

Cht nn phi c 1 tia Raman yu hoc ph hunh quang trong vng quan tm (region of interest).

Cht MgO (khong cht Periclase) c th c s dng nh lp cht nn, mc d nhng knh thytinh ngy nay vn thng c dng. N khng c ph Raman v c tnh chu nhit tt. Lp cht nnc nh bng :c th quan st thy tinh th c kch thc nhiu chnh chm tia kch thch chiu thng ln trn lp cht nnmc ch: ngn cn hin tng phn x gng (specular reflection) do s khuych tn ca tiaRaman n mu.

1 b lc khng gian: c dng gim nhng ngun giao thoa ph (spectral inference) n mcthp nht.Thit k ca my vi d c to ra nhm p ng s c lp v ng i ca tia sng (optical path) 1

cch hon ton cho bc x kch thch (excitation radiation) v bc x tn sc (scattered radiation), vsau c kt hp vi nhau bi cc tnh cht tn sc nh sng ca ht c nghin cu.3.7.2 Thc nghimHnh 3-29 : minh ha s quang hc ca thit b my vi d Spex Micramate Raman (microprobe).


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Mu kho st c t gi mu (1) ca knh hin vi v c chiu sng bng n chiu (2) . S hi ttrn mu c thc hin bng cch nhn vo im quan st (7) v iu chnh vt knh (3). n chiu (4) ctt v chm laser (5) c chiu thng n b tch chm (6). im quan st (7) c tt v my thu hnh TVc bt ln bi lng knh quay. nh sng tn x t mu kho st c thu nhn t vt knh (3) v gi nquang ph k qua khe.Trong trng hp ny, ngi ta thng s dng my d (detector) l ng nhn quangc lm lnh v h thng m photon c c nhy cao v gim thiu ting n.

Hnh 3-29, S quang hc ca quang ph k Micro-Raman Spex Micramate3.7.3 S ng dngMt vi ng dng ca my vi d Raman c trnh by sau y.My vi d Raman a ra nhng ng dng trong 1 s lnh vc khoa hc khc nhau. Thng thng, cc lnh

vc c ng dng ri vo 2 loi chnh:(1) Nhn dng du vt ca tp cht (contaminant) vi m (microscopy).(2) M t tnh cht ca vt liu mi.(a) Nhn dng b mt ca tp chtS c mt ca tp cht hu c khong 1 m hoc nhng tm film mng c 1 m trn tm bn dn Silic (l

tm bn dn silic hnh trn c to ra trong qu trnh sn xut thit b bn dn) (silicon wafer) trong sutqu trnh sn xut mch tch hp c th d dng c nhn ra. Nhng tp cht ny c th tc ng n hiu sutca thit b cho nn phi c nhn ra. Hnh 3-30 cho thy s nhn dng cc tp cht ca Teflon (Teflon l tnthng hiu dng gi thay th tn ha cht ca mt loi polymerpolytetrafluoroethylene vit tt l PTFE

do nh khoa hc Roy Plunkett (1910 1994) khm ph vo nm 1938. c tnh c o ca PTFE l h s cst (coefficient of friction) ca cht ny thp nht i vi tt c cc kim loi hin din trn tri t. y l mtha cht hu c cha floruacacbon c c tnh chu nhit v khng kt dnh dng trong ng gi, b lc, chtcch in, dng c nu n v hn ch). Nhng k thut khc, v d nh IR, nhiu x tia X, my khoan v my vid electron, u khng nhn dng c cc tp cht t nhin ny.

Hnh 3-30 Ph my vi d Raman ca tp cht Fluorur Hidrcacbon trn tm bn dn Silic c nh bngv n mn plasma (bn di) v ph Raman ca polytetra fluorethylene (bn trn).

(b) Hp cht sinh hcMy vi d Raman c dng nhn ra cc th l trong cc m khc nhau. Hnh 3-31 cho thy quang ph cahch bch huyt c kch c 5 m, thu c bng cch ly sinh thit t 1 bnh nhn. (Hch bch huyt hayhch lympho l mt trong v s cc cu trc trn, hnh bu dc dp, ri rc dc theo cc mch bch huyt. Cc

hch bch huyt c mt khp c th, tp trung nhiu mt s vng nh c, nch, bn. Hch bch huyt ngvai tr quan trng i vi hot ng ca h min dch. Cc hch bch huyt cng c ngha quan trng trongvic chn on bnh. Chng nng hoc sng ln trong nhng tnh trng khc nhau, t nh nh vim hng nnguy him nh ung th). Th l c xc nhn l 1 ht cao su silicon (Cao su tng hp lm t cht n hisilicon v c tnh cht chng tc ng ha hc, axit yu c s dng lm m v cch in) (dimethylsiloxane).

Hnh 3-31 Ph RMP thu c trong nghin cu cc th l trong lt ct sinh thit m hch bch huyt,(c) Cc th vi (inclusions) ) trong cht rn v c (bt c cht no bn trong khong vt trong qu trnh

hnh thnh nn khong vt u c gi l th vi)Cht rn, lng, kh trong t nhin c th c tm thy bn trong thy tinh v c trong sut hoc cht kt

tinh c th c xc nh bng k thut vi d Raman m khng cn lm v mu. Nhng k thut phn tch

khc, nh l khi ph hc (mass spectroscopy) hay knh hin vi in t, tng thu nhn nhiu thng tin nhngi hi phi c s ph hy mu gc. Kh nng ca my vi d rt hu dng trong vic phn tch th vi(inclusions) trong vt liu trc v sau khi x l 1 mu. Ch c s hn ch l v tr ca th vi trong vt liu

phi c nh v trong phm vi tm hot ng ca thu knh vt knh trong knh hin vi. Hnh 3-32 m t myvi d quang ph Raman o th bt kh (bubble inclusions) c to thnh do 1 s sai hng trn knh NaPO3trong qu trnh Nitro ha thy tinh vi dung dch Amoniac. Thy tinh c nitrit ha tng bn c hc.Kt qu quang ph Raman quay cho bit r rng rng dung dch amoniac cn li trong bt kh b phn lythnh phn t Nit v Hidr trong sut thi gian x l. Nu 1 pha rn mi c to thnh trn b mt ca btkh trong thi gian x l bng cch hi t chm tia laser ca my vi d ln n trong thi gian o quang ph th

bn cht ca n cng c th c xc nhn m khng cn n s ph hy mu.Hnh 3-32 (a) Ph Raman quay ca 1 bt kh trong knh (thy tinh) NaPO 3 khong 5-100 cm-1 vng nhn

thy N2, (b) Ph Raman quay ca 1 bt kh trong knh (thy tinh) NaPO3 khong 550-650 cm-1 vng nhn thyH2.

(d) S sp xp (bn ) b mt
http://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_mi%E1%BB%85n_d%E1%BB%8Bch&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Vi%C3%AAm_h%E1%BB%8Dng&action=edit&redlink=1http://vi.wikipedia.org/wiki/Ung_th%C6%B0http://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_mi%E1%BB%85n_d%E1%BB%8Bch&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Vi%C3%AAm_h%E1%BB%8Dng&action=edit&redlink=1http://vi.wikipedia.org/wiki/Ung_th%C6%B0


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Li th ca k thut my vi d Raman l c kh nng v s phn t v trng thi tinh th trn bmt ca vt mu. iu ny c hon thnh bng cch kt ni 1 bn knh hin vi iu khin bng my tnh votrong h thng phn mm. Mu vt c th c phc ha thng qua tn hiu Raman ca n vi phn giikhng gian l 1m. Bn v ny c th c thc hin bng cch kt hp chng trnh hin th 3-D vi nhngtn hiu thu c vo 1 ng nhn quang (PM) (photomultiplier) (NQ loi n in t dng khuch i nhngtia sng yu, bin thin nhanh. c s dng trong cc h truyn hnh, truyn nh v cc ng m nhp nhy) hay vi1 n bn dn Silic (ISPD) tng s tuyn tnh. Nhng ng dng s b mt bng tia Raman ang pht trin1 cch nhanh chng v k thut ny c bit thch hp cho vic nghin cu b mt ca cc mu bn dn, mngkim cng, gm v khong vt hc. Cc ng dng gm c cc vt liu sinh hc cng xut hin trn thc t.

Nhc im ca nhng h thng my vi d hin nay l nng lng tn x ca bc sng laser thp.3.7.4. Knh hin vi FT-RamanMesserschmidt v Chase gn y chng minh s tin li ca vic dng knh hin vi thu nhn hiu ng

FT-Raman. S truyn nng lng laser xy ra do s quang hc tp th trong dng c ny. Hnh 3-33 m tquang ph ca 1 si n Kevlar polymer (ng knh 12 m) khi c thc hin bng knh hin vi FT-Raman.Kevlar rt kh o c bng quang ph hc Raman thng thng v nh hng ca hiu ng hunh quang.

Gn y, hng Bruker gii thiu 1 knh hin vi FT-Raman l s thm vo ca Module FT-Raman BrukerFRA 106, 1 b phn thm vo quang ph k FT-IR. S kt hp gia knh hin vi v Module Raman c to ra

bi si quang hc NIR. Trong vng bc sng Raman kch thch th nghim bng tia laser Nd:YAG, s truyncc si quang hc mc ti a, do cho php s th nghim thnh cng. S phn gii khng gian xung 5

m c th t c. K thut ny xut hin vt thm vo knh hin vi FT-IR.3.8. Quang ph FT-Raman (179)Chuyn i quang ph theo thi gian thnh quang ph theo tn s. Bin i Fourier

Nguyn tc Trong quang ph FT Raman , cng c o ng thi ti nhiu bc sng - > quang ph

theo thi gian Ph ny sau c bin i thnh ph truyn thng nh vo php bin i Fourier

Cu to my quang ph FT - Raman

u im v hn ch ca h thng FT Ramanu im

- Gim c hunh quang- phn gii cao- C kh nng o tn s thp- Linh ng trong thc nghim

- Cc vch Stokes v an Stokes c thu nhn ng thi -> xc nh c nhit ph- s dng c IR v Raman trong cng thit bHn ch

- C s hp thu trong vng NIR
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- nhy thp- Khng th pht hin cc tp cht c hm lng ppm bng php tr ph- Cng ph thuc vo tn s- Rt kh o mu nhit ln hn 150 C

ng dnga) Ph Rhodamine - thuc nhum, pht hunh quang mnhVn hunh quang v s phn ly nhit gy rt nhiu kh khn i vi ph RAMAN thng thng btc khi no nghin cu v laser mu.

b) Nhng loi hp thu nc.c) Ph ca nhng nguyn t quan trn v mt sinh hcVt cht sinh hc thng gy nhiu kh khn trong ph Raman thng thng. Vn xut pht thunh quang trn vt, nh l nhng vt nt t nhin v tn x n hi trn phng nn ca cc mu vt.d) Nhn dng php l thuc cm v cht gy n.Ph Raman thng thng khng nhn ra do phng nn ln v mt nhiu thi gian.e) Mu polymerVn hunh quang l mi nguy hi trong nghin cu cc loi polymer khc nhau.f) Chun on bnh l trong y hcNguyn l

Ph Raman thng thng o cng so vi tn s hoc s sng. K thut FT, o cng ca nhsng ca nhiu bc sng cng 1 lc. Sau c chuyn thnh quang ph theo thi gian. Ph c

bin i thnh ph thng thng bng cch ly trung bnh ca bin i Fourier s dng chng trnhmy tnh. Dng sng FT-Raman thc nghim. c trng ca ph FT-Raman ging ph FT-IR l thyton b bc sng mi thi gian.

cac phuong phap pho raman (1)

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