optical1_lect21

7/21/2019 optical1_lect21

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Optical Properties I:Optical Properties I:

Color – Pigments andColor – Pigments andGemstonesGemstones

Chemistry 754Chemistry 754Solid State ChemistrySolid State Chemistry

Lecture #!Lecture #!

"ay !$ %%&"ay !$ %%&



'lectromagnetic (adiation and'lectromagnetic (adiation andthe )isi*le Spectrumthe )isi*le Spectrum

UVUV 100-400 nm100-400 nm 12.4 - 3.10 eV12.4 - 3.10 eVVioletViolet 400-425 nm400-425 nm 3.10 - 2.92 eV3.10 - 2.92 eVBlueBlue 425-492 nm425-492 nm 2.92 - 2.52 eV2.92 - 2.52 eVGreenGreen 492-575 nm492-575 nm 2.52 - 2.15 eV2.52 - 2.15 eVYellowYellow 575-585 nm575-585 nm 2.15 - 2.12 eV2.15 - 2.12 eVOrangeOrange 585-647 nm585-647 nm 2.12 - 1.92 eV2.12 - 1.92 eV

e!e! 647-700 nm647-700 nm 1.92 - 1.77 eV1.92 - 1.77 eV"ear #"ear # 10$000-700 nm10$000-700 nm 1.77 - 0.12 eV1.77 - 0.12 eV

#% a&'or&an(e o((ur' in one region o% t)e (olor w)eel t)e material a**ear'#% a&'or&an(e o((ur' in one region o% t)e (olor w)eel t)e material a**ear'wit) t)e o**o'ite +(om*limentar, (olor. or e/am*lewit) t)e o**o'ite +(om*limentar, (olor. or e/am*le

a material a&'or&' iolet lig)ta material a&'or&' iolet lig)t →→ olor Yellowolor Yellow a material a&'or&' green lig)ta material a&'or&' green lig)t →→ olor e!olor e! a material a&'or&' iolet$ &lue greena material a&'or&' iolet$ &lue green →→ olor Orange-e!olor Orange-e! a material a&'or&' re!$ orange ,ellowa material a&'or&' re!$ orange ,ellow →→ olor Blueolor Blue

)( )(λλ +4.1357 / 10 +4.1357 / 10-15-15 eV-'+2.998 / 10eV-'+2.998 / 1088 m'm'λλ +eV 1240 +eV 1240λλ+nm+nm

(ed(ed

OrangeOrange

+ello, +ello, GreenGreen

-lue-lue

)iolet)iolet



Color in '.tended Inorganic SolidsColor in '.tended Inorganic Solids: Intratomic /Locali0ed1 e.citationsIntratomic /Locali0ed1 e.citations

rr3;3; Gem'tone' +i.e. rGem'tone' +i.e. r3;3; in u&, an! meral!in u&, an! meral! Blue an! Green uBlue an! Green u2;2; (om*oun!' +i.e. mala()ite$ tur<uoi'e(om*oun!' +i.e. mala()ite$ tur<uoi'e

Blue oBlue o2;2; (om*oun!' +i.e. =l(om*oun!' +i.e. =l22oOoO44$ a>urite$ a>urite

: Charge2trans3er e.citations /metal2metal$ anion2metal1Charge2trans3er e.citations /metal2metal$ anion2metal1 ee2;2; →→ ?i?i4;4; in 'a**)irein 'a**)ire

ee2;2; →→ ee3;3; in @ru''ian Bluein @ru''ian Blue

OO2-2- →→ rr6;6; in BarOin BarO44

: )alence to Conduction -and ransitions in Semiconductors)alence to Conduction -and ransitions in Semiconductors AOAO33 +Yellow+Yellow

! +Yellow !e +Bla(C! +Yellow !e +Bla(C

Dg +inna&ar - e! Dg +meta(inna&ar - Bla(CDg +inna&ar - e! Dg +meta(inna&ar - Bla(C

: Intra*and e.citations in "etalsIntra*and e.citations in "etals trong a&'or*tion wit)in a *artiall, %ille! &an! lea!' to metalli( lu'tre ortrong a&'or*tion wit)in a *artiall, %ille! &an! lea!' to metalli( lu'tre or

&la(C (oloration&la(C (oloration



-and to -and ransitions-and to -and ransitionsOptical Properties o3 SemiconductorsOptical Properties o3 SemiconductorsAe (an e/amine t)e relation')i*Ae (an e/amine t)e relation')i*

&etween &on!ing +'*atial an!&etween &on!ing +'*atial an!energeti( oerla* an! o*ti(alenergeti( oerla* an! o*ti(al

*ro*ertie' &, (on'i!ering t)e &an!-*ro*ertie' &, (on'i!ering t)e &an!-ga*' o% t)o'e (om*oun!' w)i()ga*' o% t)o'e (om*oun!' w)i()

a!o*t t)e *)alerite 'tru(ture$ wit)a!o*t t)e *)alerite 'tru(ture$ wit)all ion' in tetra)e!ral (oor!inationall ion' in tetra)e!ral (oor!ination+'ee %igure to t)e rig)t.+'ee %igure to t)e rig)t.

in(e ele(troni( tran'ition' %romin(e ele(troni( tran'ition' %romt)e alen(e to (on!u(tion &an! '*ant)e alen(e to (on!u(tion &an! '*an

a %airl, large range o% energie'$a %airl, large range o% energie'$'emi(on!u(tor' a(t a' 'ort o% a long'emi(on!u(tor' a(t a' 'ort o% a long*a'' %ilter +onl, re%le(ting lig)t wit)*a'' %ilter +onl, re%le(ting lig)t wit)energ, le'' t)an t)e &an! ga*. ?)i'energ, le'' t)an t)e &an! ga*. ?)i'(an gie ri'e to onl, (ertain (olor'.(an gie ri'e to onl, (ertain (olor'.

-and Gap /e)1-and G

ap /e)1 ColorColor '.ample'.am

ple &6% hite

8nO &6%265 +ello, CdS 6&265 Orange GaP !6926& (ed gS ; !69 -lac< CdSe



Spatial O=erlap and -and Gap /'Spatial O=erlap and -and Gap /'gg11

A)at are t)e e%%e(t' o% in(rea'ing t)e '*atial oerla*E Van-A)at are t)e e%%e(t' o% in(rea'ing t)e '*atial oerla*E Van-

Ve()ten @)illi*' a''ume! '*atial oerla* i' *ro*ortional to !Ve()ten @)illi*' a''ume! '*atial oerla* i' *ro*ortional to !-2.5-2.5

+w)ere ! i' t)e &on! !i'tan(e.+w)ere ! i' t)e &on! !i'tan(e.

:Primary '33ectPrimary '33ect #n(rea'e' t)e oerall energ, leel o% t)e #n(rea'e' t)e oerall energ, leel o% t)e(on!u(tion &an! +more )ig)l, anti&on!ing F(on!u(tion &an! +more )ig)l, anti&on!ing Fgg ↑↑

:Secondary '33ectSecondary '33ect #n(rea'e' t)e &an!wi!t) F #n(rea'e' t)e &an!wi!t) Fgg ↓↓

Conduction -andConduction -and/>nti*onding1/>nti*onding1

)alence -and)alence -and/-onding1/-onding1

''gg ''gg



Ionicity and -and Gap /'Ionicity and -and Gap /'gg11

A)at are t)e e%%e(t' o% in(rea'ing t)e ele(tronegatiit,A)at are t)e e%%e(t' o% in(rea'ing t)e ele(tronegatiit,

!i%%eren(e &etween t)e element'E!i%%eren(e &etween t)e element'E:Primary '33ectPrimary '33ect #n(rea'e' t)e 'e*aration o% t)e alen(e an! #n(rea'e' t)e 'e*aration o% t)e alen(e an!(on!u(tion &an!' +t)e &on!' &e(ome more ioni( F(on!u(tion &an!' +t)e &on!' &e(ome more ioni( Fgg ↑↑

:Secondary '33ectsSecondary '33ects He(rea'e' t)e &an!wi!t) F He(rea'e' t)e &an!wi!t) Fgg ↑↑ an! an!

re!u(e' t)e (oalent anti&on!ing !e'ta&ili>ation Fre!u(e' t)e (oalent anti&on!ing !e'ta&ili>ation Fgg ↓↓

Conduction -andConduction -and/>nti*onding1/>nti*onding1

)alence -and)alence -and/-onding1/-onding1

''gg''gg



'nergetic ? Spatial O=erlap'nergetic ? Spatial O=erlap

SiSi d@6&5 Ad@6&5 A >lP>lP d@6&7 Ad@6&7 A @%@% @%6@%6GeGed@644 Ad@644 A Ga>sGa>s d@645 Ad@645 A 8nSe8nSe d@645 Ad@645 A

@%@% @%64&@%64& @%6B%@%6B%SnSn d@69! Ad@69! A InS*InS* d@69% Ad@69% A CdeCde d@69! Ad@69! A

@%@% @%6&!@%6&! @%6!@%6!

'.perimental -and Gaps '.perimental -and Gaps

SiSi !6! e)!6! e) >lP>lP 645 e)645 e)GeGe %67 e)%67 e) Ga>sGa>s !64 e)!64 e) 8nSe8nSe 69 e)69 e)SnSn %6%9 e)%6%9 e) InS*InS* %6!7 e)%6!7 e) CdeCde !64 e)!64 e)

Constant Spatial O=erlapConstant Spatial O=erlap

Increasing Ionicity /'Increasing Ionicity /'gg ↑11

ecreasing Spatial O=erlap /'ecreasing Spatial O=erlap /'gg ↓11Slo,ly ecreasing Ionicity /'Slo,ly ecreasing Ionicity /'gg ↓11

>l>l SiSi PP

GaGa

InIn

GeGe

SnSn

>s>s

S*S* ee

SeSe

CdCd

8n8n



Colored SemiconductorsColored Semiconductors

CdS /'CdS /'gg@64 e)1@64 e)1 Cde /'Cde /'gg@!65% e)1@!65% e)1

8nSe /'8nSe /'gg@659 e)1@659 e)18nS /'8nS /'gg@&6 e)1@&6 e)1

Ae 'ee t)at a' t)e &an!Ae 'ee t)at a' t)e &an!ga* !e(rea'e' a' eit)erga* !e(rea'e' a' eit)erele(tronegatiit, o% t)eele(tronegatiit, o% t)eanion !e(rea'e' +!anion !e(rea'e' +! →→

!?e$ In!?e$ In →→ Ine or t)eIne or t)eoerla* !e(rea'e' +Inoerla* !e(rea'e' +In →→

!.!.

=l'o note t)at (olore!=l'o note t)at (olore!(om*oun!' onl, re'ult w)en(om*oun!' onl, re'ult w)en1.8J1.8JggJ3.0. Karger ga*' gieJ3.0. Karger ga*' gie

w)itetran'*arent w)itetran'*arent 'maller ga*' gie &la(C.'maller ga*' gie &la(C.

http://www.ii-vi.com/images/prod-images/material-znse.JPG

http://www.asarco.com/products99/images99/cadmium_sulfide.jpg



B, %orming 'oli! 'olution' o% !i%%erent 'emi(on!u(tor' ele(tri(al engineer' are a&le toB, %orming 'oli! 'olution' o% !i%%erent 'emi(on!u(tor' ele(tri(al engineer' are a&le to!e'ign material' an! Lun(tion' wit) '*e(i%i( &an! ga*'. ?)i' a**roa() o%ten (alle!!e'ign material' an! Lun(tion' wit) '*e(i%i( &an! ga*'. ?)i' a**roa() o%ten (alle!

&an! ga* engineering i' u'e! to %a&ri(ate a num&er o% !ei(e'$ 'u() a' KHM'$&an! ga* engineering i' u'e! to %a&ri(ate a num&er o% !ei(e'$ 'u() a' KHM'$'emi(on!u(tor +!io!e$ )eteroLun(tion$ <uantum well la'er'$ *)oto!ete(tor'$ 'olar (ell'$'emi(on!u(tor +!io!e$ )eteroLun(tion$ <uantum well la'er'$ *)oto!ete(tor'$ 'olar (ell'$et(. #n t)i' %iel! it i' im*ortant to (on'i!er +a t)e &an! ga* o% t)e two en! mem&er'$et(. #n t)i' %iel! it i' im*ortant to (on'i!er +a t)e &an! ga* o% t)e two en! mem&er'$

+& t)e latti(e mat() &etween material'$ +( !ire(t '. in!ire(t ga* material'.+& t)e latti(e mat() &etween material'$ +( !ire(t '. in!ire(t ga* material'.

igure' taCen %rom Nemi(on!u(torO*toele(troni( Hei(e'$ &, @. B)atta()ar,a

eteroDunction laser

he Ga>s /'g@!64 e)$ a@565>1 :

>l>s /'g@6! e)$ a@56>1 isamong the most important 3oroptoelectronic de=ices$ *ecause o3the e.cellent lattice matching6

-andgap 'ngineering-andgap 'ngineering



orwar! &ia' at a *-n Lun(tion %or(e'orwar! &ia' at a *-n Lun(tion %or(e'minorit, (arrier' a(ro'' t)e Lun(tion. ?)i'minorit, (arrier' a(ro'' t)e Lun(tion. ?)i'(au'e' ele(tron' to %all into a(ant )ole'(au'e' ele(tron' to %all into a(ant )ole'ra!iatiel,$ giing o%% lig)t. Ho*ant' arera!iatiel,$ giing o%% lig)t. Ho*ant' are

im*ortant 'ite' %or lo(ali>ing (arrier'$ t)u'im*ortant 'ite' %or lo(ali>ing (arrier'$ t)u'tran'ition' are o%ten Btran'ition' are o%ten B →→ a((e*tor$ ora((e*tor$ or

!onor!onor →→

VBVBCommon L' materialsCommon L' materials

:Ga>s /'Ga>s /'gg@!64& e)1@!64& e)1→ Eear I(Eear I(

:GaP:E /'GaP:E /'gg @ 65 e)1@ 65 e)1→ +ello, +ello,

:GaP:8n$O /'GaP:8n$O /'gg @ 65 e)1@ 65 e)1→ (ed(ed

:GaE$ SiCGaE$ SiC → -lue-lue

Light 'mitting iodesLight 'mitting iodes



CrCr&F&F GemstonesGemstones/(itation o% an ele(tron %rom one !-or&ital to anot)er !-or&ital on t)e 'ame/(itation o% an ele(tron %rom one !-or&ital to anot)er !-or&ital on t)e 'ame

atom o%ten time' gie' ri'e to a&'or*tion in t)e i'i&le region o% t)eatom o%ten time' gie' ri'e to a&'or*tion in t)e i'i&le region o% t)e'*e(trum. ?)e r'*e(trum. ?)e r3;3; ion in o(ta)e!ral (oor!ination i' a er, intere'tingion in o(ta)e!ral (oor!ination i' a er, intere'tinge/am*le o% t)i'. lig)t ()ange' in itM' enironment lea! to ()ange' in t)ee/am*le o% t)i'. lig)t ()ange' in itM' enironment lea! to ()ange' in t)e'*litting o% t)e t'*litting o% t)e t2g2g an! ean! egg or&ital'$ w)i() ()ange' t)e (olor t)e material.or&ital'$ w)i() ()ange' t)e (olor t)e material.

Den(e$ rDen(e$ r3;3; im*uritie' are im*ortant in a num&er o% gem'tone'.im*uritie' are im*ortant in a num&er o% gem'tone'.

(u*y(u*y>l>lOO&&:Cr:Cr&F&F

'merald'merald-e-e>l>lSiSiOO!9!9

:Cr:Cr&F&F

SunlightSunlight Incandescent lightIncandescent light

>le.andrite>le.andrite-e>l-e>lOO44:Cr:Cr&F&F



CrCr&F&F GemstonesGemstones/(itation o% an ele(tron %rom one !-or&ital to anot)er !-or&ital on t)e 'ame/(itation o% an ele(tron %rom one !-or&ital to anot)er !-or&ital on t)e 'ame

atom o%ten time' gie' ri'e to a&'or*tion in t)e i'i&le region o% t)eatom o%ten time' gie' ri'e to a&'or*tion in t)e i'i&le region o% t)e'*e(trum. ?)e r'*e(trum. ?)e r3;3; ion in o(ta)e!ral (oor!ination i' a er, intere'tingion in o(ta)e!ral (oor!ination i' a er, intere'tinge/am*le o% t)i'. lig)t ()ange' in itM' enironment lea! to ()ange' in t)ee/am*le o% t)i'. lig)t ()ange' in itM' enironment lea! to ()ange' in t)e'*litting o% t)e t'*litting o% t)e t2g2g an! ean! egg or&ital'$ w)i() ()ange' t)e (olor t)e material.or&ital'$ w)i() ()ange' t)e (olor t)e material.

Den(e$ rDen(e$ r3;3; im*uritie' are im*ortant in a num&er o% gem'tone'.im*uritie' are im*ortant in a num&er o% gem'tone'.

(u*y >le.andrite 'meraldost Corundum

>lO&

Chryso*eryl-e>lO4

-eryl-e&>lSiO!9

tg–eg Splitting 6& e) 6!7 e) 6%5 e)

Color (ed Blue-Green +Ha,lig)te! +an!lelig)t

Green



CrCr&F&F Gemstones2ost StructuresGemstones2ost Structures

#n ea() o% t)e t)ree gem'tone' r#n ea() o% t)e t)ree gem'tone' r3;3;

im*uritie' 'u&'titute %or =lim*uritie' 'u&'titute %or =l3;3;

ononan o(ta)e!ral 'ite.an o(ta)e!ral 'ite.

CorundumCorundum>l>lOO&&

-eryl-eryl-e-e&&>l>lSiSiOO!9!9



erm Sym*olserm Sym*ols

?erm ',m&ol' are ')ort)an! notation %or re*re'enting t)e ele(tron?erm ',m&ol' are ')ort)an! notation %or re*re'enting t)e ele(tron(on%iguration o% a lo(ali>e! ion.(on%iguration o% a lo(ali>e! ion.

2;12;1KKPP

?)e total '*in <uantum Q o% t)e atomion +Cee* in min! t)at ?)e total '*in <uantum Q o% t)e atomion +Cee* in min! t)atea() ele(tron )a' a '*in angular momentum o% ;R or -Rea() ele(tron )a' a '*in angular momentum o% ;R or -R K ?)e total angular momentum <uantum QK ?)e total angular momentum <uantum Q P K;P K;

ee an, a!an(e! inorgani( ()emi'tr, te/t %or a !e'(ri*tion o% termee an, a!an(e! inorgani( ()emi'tr, te/t %or a !e'(ri*tion o% term',m&ol'. Ae will (on(entrate on t)e '*in alue$ a' it (an ea'il, &e',m&ol'. Ae will (on(entrate on t)e '*in alue$ a' it (an ea'il, &e

inter*rete! to !etermine t)e num&er o% un*aire! ele(tron'.inter*rete! to !etermine t)e num&er o% un*aire! ele(tron'.ransitions ,here the total spin changes reuire at least oneransitions ,here the total spin changes reuire at least oneelectron to re=erse itHs spin6 Such transitions are called spinelectron to re=erse itHs spin6 Such transitions are called spin

3or*idden transitions6 hey are =ery ,ea< transitions63or*idden transitions6 hey are =ery ,ea< transitions6



una*e2Sugano iagram Cruna*e2Sugano iagram Cr&F&F

ttgg

eegg

ttgg

eegg

ttgg

eegg

44!! ?? 44 StatesStates

44

>> Ground StateGround State

''!! StateState

Spin>llo,edransition

?)e ?una&e-ugano !iagram &elow ')ow' t)e allowe! ele(troni( e/(itation' %or r?)e ?una&e-ugano !iagram &elow ')ow' t)e allowe! ele(troni( e/(itation' %or r 3;3;

in an o(ta)e!ral (r,'tal %iel! +in an o(ta)e!ral (r,'tal %iel! +44==22 →→ 44? ? 11 44==22 →→ 44? ? 22. ?)e !otte! erti(al line ')ow'. ?)e !otte! erti(al line ')ow't)e 'trengt) o% t)e (r,'tal %iel! '*litting %or rt)e 'trengt) o% t)e (r,'tal %iel! '*litting %or r3;3; in =lin =l22OO33. ?)e. ?)e 44==22 →→ 44? ? 11 energ,energ,

!i%%eren(e (orre'*on!' to t)e '*litting &etween t!i%%eren(e (orre'*on!' to t)e '*litting &etween t 2g2g an! ean! egg



(u*y (ed(u*y (ed?)i' %igure +taCen %rom N?)e @),'i(' an! )emi'tr, o% olor$ &, Surt?)i' %igure +taCen %rom N?)e @),'i(' an! )emi'tr, o% olor$ &, Surt

"a''au ')ow' t)e two '*in allowe! tran'ition' %or r"a''au ')ow' t)e two '*in allowe! tran'ition' %or r 3;3; in ru&, gie ri'e toin ru&, gie ri'e toa&'or*tion in t)e iolet an! t)e green. in(e t)e tran'mi''ion in t)e re! i'a&'or*tion in t)e iolet an! t)e green. in(e t)e tran'mi''ion in t)e re! i'mu() more t)an t)e tran'mi''ion in t)e &lue ru&ie' are re!. ?)emu() more t)an t)e tran'mi''ion in t)e &lue ru&ie' are re!. ?)e 22 →→ 44==22

%luore'(en(e a!!' to t)e !ee* re! (olor o% a ru&,.%luore'(en(e a!!' to t)e !ee* re! (olor o% a ru&,.



'merald Green'merald Green?)i' %igure +al'o taCen %rom N?)e @),'i(' an! )emi'tr, o% olor$ &, Surt?)i' %igure +al'o taCen %rom N?)e @),'i(' an! )emi'tr, o% olor$ &, Surt

"a''au ')ow' t)e tran'ition' %or r"a''au ')ow' t)e tran'ition' %or r3;3; in &er,l. ?)e (r,'tal %iel! '*litting i'in &er,l. ?)e (r,'tal %iel! '*litting i'

a little &it 'maller t)an ru&,$ 'o t)at t)e lower energ, a&'or*tion i' ')i%te!a little &it 'maller t)an ru&,$ 'o t)at t)e lower energ, a&'or*tion i' ')i%te!to lower energ, taCing out mu() o% t)e re%le(tan(e o% re! lig)t an! ()angingto lower energ, taCing out mu() o% t)e re%le(tan(e o% re! lig)t an! ()anging

t)e (olor to green.t)e (olor to green.



he >le.andrite '33ecthe >le.andrite '33ect

=le/an!rite +Be=l=le/an!rite +Be=l22OO44rr3;3; )a' a (r,'tal %iel! '*litting$ 2.17 eV$ )a' a (r,'tal %iel! '*litting$ 2.17 eV$interme!iate &etween ru&, +=linterme!iate &etween ru&, +=l22OO33 - 2.23 eV an! Ber,l +Be- 2.23 eV an! Ber,l +Be33=l=l22ii66OO1818 - 2.07 eV. ?)u' it )a' 'ome tran'mittan(e in t)e re! an! a %airl,- 2.07 eV. ?)u' it )a' 'ome tran'mittan(e in t)e re! an! a %airl,

large tran'mittan(e in t)e &lue-green region o% t)e '*e(trum. ?)i'large tran'mittan(e in t)e &lue-green region o% t)e '*e(trum. ?)i'lea!' to er, intere'ting (olor an! o*ti(al *ro*ertie'.lea!' to er, intere'ting (olor an! o*ti(al *ro*ertie'.

#n t)e *re'en(e o% re!!i') lig)t$ a' %rom a (an!le or an in(an!e'(ent#n t)e *re'en(e o% re!!i') lig)t$ a' %rom a (an!le or an in(an!e'(entlig)t 'our(e$ it i' !ee* re! in (olor. e'em&ling a ru&,.lig)t 'our(e$ it i' !ee* re! in (olor. e'em&ling a ru&,.

#n t)e *re'en(e o% lig)t wit) a maLor (om*onent in t)e &lueUV#n t)e *re'en(e o% lig)t wit) a maLor (om*onent in t)e &lueUVregion o% t)e '*e(trum$ 'u() a' 'unlig)t or %luore'(ent lig)t$ t)eregion o% t)e '*e(trum$ 'u() a' 'unlig)t or %luore'(ent lig)t$ t)e

re%le(tan(e in t)e &lue-green region o% t)e '*e(trum !ominate' an!re%le(tan(e in t)e &lue-green region o% t)e '*e(trum !ominate' an!ale/an!rite re'em&le' an emeral!.ale/an!rite re'em&le' an emeral!.



CuCuFF ransitionsransitions

?)e !?)e !99 (on%iguration o% u(on%iguration o% u2;2;$ lea!' to$ lea!' toa Pa)n-?eller !i'tortion o% t)ea Pa)n-?eller !i'tortion o% t)e

regular o(ta)e!ral geometr,$ an!regular o(ta)e!ral geometr,$ an!'et' u* a %airl, low energ, e/(itation'et' u* a %airl, low energ, e/(itation

%rom !%rom !/ / 2 2 -, -, 2 2 leel to a !leel to a !> > 2 2 leel. #%leel. #%t)i' a&'or*tion %all' in t)e re! ort)i' a&'or*tion %all' in t)e re! or

orange region' o% t)e '*e(trum$ aorange region' o% t)e '*e(trum$ agreen or &lue (olor (an re'ult. omegreen or &lue (olor (an re'ult. omenota&le e/am*le' in(lu!enota&le e/am*le' in(lu!e

"alachite /green1"alachite /green1CuCuCOCO&&/O1/O1

uruoise /*lue2green1uruoise /*lue2green1Cu>lCu>l/PO/PO441/O11/O19944OO

>0urite /*lue1>0urite /*lue1

CuCu&&/CO/CO&&11/O1/O1

Ground

State

'.citedState

Pseudo tPseudo tgg

dd. . 2y 2y

dd0 0

Pseudo tPseudo tgg

dd. .

2y 2y

dd0 0



Charge rans3er in SapphireCharge rans3er in Sapphire?)e !ee* &lue (olor t)e gem'tone 'a**)ire i' al'o?)e !ee* &lue (olor t)e gem'tone 'a**)ire i' al'o

&a'e! on im*urit, !o*ing into =l&a'e! on im*urit, !o*ing into =l22OO33. ?)e (olor in. ?)e (olor in'a**)ire ari'e' %rom t)e %ollowing ()arge tran'%er'a**)ire ari'e' %rom t)e %ollowing ()arge tran'%ere/(itatione/(itation

ee2;2; ; ?i; ?i4;4; →→ e e3;3; ; ?i; ?i3;3; + +λλma/ma/ T 2.2 eV$ 570 nmT 2.2 eV$ 570 nm

?)e tran'ition i' %a(ilitate! &, t)e geometr, o% t)e?)e tran'ition i' %a(ilitate! &, t)e geometr, o% t)e(orun!um 'tru(ture w)ere t)e two ion' ')are an(orun!um 'tru(ture w)ere t)e two ion' ')are ano(ta)e!ral %a(e$ w)i() allow' %or %aora&le oerla* o%o(ta)e!ral %a(e$ w)i() allow' %or %aora&le oerla* o%t)e !>t)e !>22 or&ital'.or&ital'.:UnliCe t)e !-! tran'ition in u&,$ t)e ()arge-tran'%erUnliCe t)e !-! tran'ition in u&,$ t)e ()arge-tran'%ere/(itation in 'a**)ire i' %ull, allowe!. ?)ere%ore$ t)ee/(itation in 'a**)ire i' %ull, allowe!. ?)ere%ore$ t)e(olor in 'a**)ire re<uire' onl, T 0.01 im*uritie'$(olor in 'a**)ire re<uire' onl, T 0.01 im*uritie'$

w)ile T 1 im*urit, leel i' nee!e! in ru&,.w)ile T 1 im*urit, leel i' nee!e! in ru&,.:#n t)e mineral ilmenite$ e?iO#n t)e mineral ilmenite$ e?iO33$ all o% t)e =l$ all o% t)e =l3;3; )a')a'&een re*la(e! &, e&een re*la(e! &, e2;2;?i?i4;4;. ?)e a&'or*tion &an!. ?)e a&'or*tion &an!&roa!en' out an! t)e (olor &e(ome' &la(C.&roa!en' out an! t)e (olor &e(ome' &la(C.



>nion to "etal Charge rans3er>nion to "etal Charge rans3er"ormall, ()arge tran'%er tran'ition' %rom an anion +i.e. O"ormall, ()arge tran'%er tran'ition' %rom an anion +i.e. O 2-2- DOO DOOto a (ation KUO %all in t)e UV region o% t)e '*e(trum an! !o notto a (ation KUO %all in t)e UV region o% t)e '*e(trum an! !o notgie ri'e to (olor. Doweer$ !gie ri'e to (olor. Doweer$ !00 (ation' in )ig) o/i!ation 'tate' are(ation' in )ig) o/i!ation 'tate' are<uite ele(tronegatie lowering t)e energ, o% t)e tran'ition metal<uite ele(tronegatie lowering t)e energ, o% t)e tran'ition metal&a'e! KUO. ?)i' moe' t)e tran'ition into t)e i'i&le region o%&a'e! KUO. ?)i' moe' t)e tran'ition into t)e i'i&le region o%t)e '*e(trum. ?)e 'trong (oalen(, o% t)e metal-o/,gen &on! al'ot)e '*e(trum. ?)e 'trong (oalen(, o% t)e metal-o/,gen &on! al'o'trongl, %aor' tetra)e!ral (oor!ination$ giing ri'e to a 'tru(ture'trongl, %aor' tetra)e!ral (oor!ination$ giing ri'e to a 'tru(ture(ontaining i'olate! O(ontaining i'olate! O44n-n- tetra)e!ra. ome e/am*le' o% t)i' are a'tetra)e!ra. ome e/am*le' o% t)i' are a'

%ollow'%ollow'

CaCa&&/)O/)O4411 /tetrahedral )/tetrahedral )5F5F11 Color @ hiteColor @ hite

P*CrOP*CrO44 /tetrahedral Cr/tetrahedral CrFF

11 Color @ +ello,Color @ +ello,CaCrOCaCrO44 ? J? JCrOCrO44 /tetrahedral Cr/tetrahedral CrFF11 Color @ +ello,Color @ +ello,P*"oOP*"oO44 /tetrahedral "o/tetrahedral "oFF11 Color @ +ello,Color @ +ello, J"nOJ"nO44 /tetrahedral "n/tetrahedral "n7F7F11 Color @ "aroonColor @ "aroon

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