Photoemission Spectroscopy Fundamental Aspects

Transcription

1 Photoemission Spectoscopy Fundamental Aspects G. Stefani Dipatimento di Fisica E. Amaldi, Univesita Roma Te CISM Unita di Riceca di Roma 3 School G. Stefani 1

2 hν Basic Concepts - E, e K e εˆ E MAX e = hν Φ School G. Stefani

3 outline 1.Intuduction.Enegy consevation, binding enegy and photoelecton enegy 3.Satellite stuctues and multiplet splitting 4.Chemical shift 5.Molecula photoelecton specta 6.Photoelecton angula distibutions 7.Hole sate elaxation 8.Resonant photoemission School G. Stefani 3

4 Photoemission Schematics: He Iα=1.3eV He IIα=40.8eV Mg Kα1, = 153,6 ev Al Kα1,=1486,6eV Synchoton Radiation hν Ω E e Amp. Counte Jehν,Ee,θ,φ,σ θ,φ,σ School G. Stefani 4

5 EERGY COSERVATIO, BIDIG EERGY AD PHOTOELECTRO EERGY E kin = hω φ E b E kin = p m p = mekin School G. Stefani 5

6 X-section vs. Photoemission cuent J e dσ hν, ϑ, φ = J h l ν ρ Fan E, Ω ηdet dωde E Ω E dωde Photoemission peak lineshape 1. Photon monochomaticity Gaussian. Electon analyze esolution Gaussian 3. Final state lifetime uncetainty pinciple Loentian Lineshape =Convolution 1,,3 School G. Stefani 6

7 The photoemission pocess φ E e = h ν BE ev s ε p hν 1s 1 Ψ a S 0 1 Ψ a 1s S 0 φ 1 School G. Stefani 7

8 School G. Stefani 8 Inteaction adiation matte ˆ 4 ν δ ε ν α π ν σ h E E h dh d A B B A i i B Ψ Ψ = Betoni s lectue this school Initial state A = eutal goundexcited state Final state B = Residual ion fee electons

9 Enegy balance fo e atom ˆ E = E B A hν Ψ Aφ φ A = Ψ = Aφ ε 1 B 1 ˆ E 1 E = E E s e 1s 1s hν E e = hν BE 4.6eV 1 s One single photoemission peak is expected Enegy and momentum ae conseved School G. Stefani 9

10 Complexity of the photoemission spectum Satellite stuctues n=1 Main peak J e x0.05 4,6 P hotoelecton E negy E e ev 95 School G. Stefani 10

11 The noble gas panoama School G. Stefani 11

12 Pimay photoionization pocess School G. Stefani 1

13 Photon = single paticle opeato o moe paticles involved in final state = e-e coelation Relaxation & e-e coelation in photoemission = satellite hν e ph [ ε ] hν - E i E f* I ε hν - E i E f [ ε ] School G. Stefani 13

14 The He satellite stuctue Ekin=hv-BE School G. Stefani 14

15 School G. Stefani 15 A many electon atom 0 A A A E H Ψ = Ψ i i j j i ij i i s l e Ze m p o s H e e H n e H kin H H = = = > ζ ;, 1 Ψ = Ψ R i i j A A σ φ ' 0 B B B E H Ψ = Ψ Single paticle obital

16 School G. Stefani 16 sudden appoximation ; ˆ 1 Ψ = Ψ B l B A ε Ψ Ψ Ω B A A B e R B j j j j l e h E E E h de d d, 1 1 1, ˆ 1 ν δ σ φ ε ε ν σ fozen coe appovimation 0 ' 0 H H = Ω B A j e j j j j l e h E h de d d,, ˆ 1 ν ε δ σ φ ε ε ν σ

17 Total photoemission coss section He Xe 1s 4d 1s Theshold 4d Theshold School G. Stefani 17

18 School G. Stefani 18 Photoelecton cuent vs. photoelecton enegy ' ',... 4, 3, 1,... 4, 3, l l l l l l l l l l l ε ε ε ε ε ν ε ε ε ε ε ν ε ν = = = = = = = He p He p He p He s He h He s He s He s He s He h s He s He h n=1 95 Monopole and dipole selection ules

19 Koopmans enegy vs. photoemission peaks I ε ε k ε [ ε ] k E i = elax i = ε ε I i I i i adiab ε k shake-off shake-up adiabatic School G. Stefani 19

20 Fom cental to peiodic potential E K School G. Stefani 0

21 Spin obit splitting Xe 4d hν =7 ev E l i s i. This is paticulaly evident in the case of the 3d Xe doublet. This is a typical final state effect. In these closed shell atoms the initial state enegy doesn t depend upon spin momentum pojections as all obitals ae fully occupied. On the contay, when e vacancy is ceated in the obital identified by n,l,m quantum numbes, the enegy of the final state depend on the 3 spin pojection mev though the tem H 0 s-o of the Hamiltonian 5. Hence, it is to be expected that holes in p l=1 and d l= will geneate doublets of final states chaacteized by quantum numbe j j=ls equal to 1/, 3/ and 7 mev /, 5/ espectively. Dettaglio Xe 3d School G. Stefani 1

22 Molecula multiplet splitting O School G. Stefani

23 MnF multiplet splitting School G. Stefani 3

24 CuCl multiplet & satellite School G. Stefani 4

25 Chemical shift C 1s ev O 1s ev C 1s CO 98 ev C 1s CH 4 91 ev School G. Stefani 5

26 Chemical shift vs.electonegativity School G. Stefani 6

27 Sensitivity to the local envionmentin fee clustes J. Chem. Phys., Vol. 10, o. 1, 1 Januay 004 Tchaplyguine et al. School G. Stefani 7

28 PES spectum of School G. Stefani 8

29 Diatomic molecule e levels LUMO HOMO School G. Stefani 9

30 Expeimental PE spectum of, and MOs School G. Stefani 30

31 Coe PE vibational spectum K. Siegbahn et al ESCA Applied to fee molecules School G. Stefani 31

32 School G. Stefani 3 Molecula PE x-section > > = = = M j i ij j i i i j j i ij i i Z Z e s l e Ze m p n n H o s H e e H n e H kin H H ζ Bon Oppenheime Ψ Ψ Ω B A R B A A A j l e C h de d d, 1 1 ˆ 1 λ λ λφ ε ε ν σ 1 δ hν E E E A B e vib A vib B Ψ Ψ vib B A B A B A,,, Ψ Ψ = Ψ

33 Fank Condon Factos School G. Stefani 33

34 PE O vibational and multiplet splitting School G. Stefani 34

35 Rotational stuctue HF School G. Stefani 35

36 Jahn Telle splitting School G. Stefani 36

37 School G. Stefani 37 PE angula distibution Ψ Ψ Ω B A R B j j j j l h d d, 1 1, ˆ 1 σ φ ε ε ν σ εˆ εˆ dω, φ θ - e e K E, hν

38 Angula distibutions εˆ dσ dω σ 4Π [ 1 βp cos ] ϑ School G. Stefani 38

39 dω J e = Φ diect Φ i i scatteed hν εˆ θ, φ E, K - e e θ φ Je, d Φ0 ΦS Φ S εˆ J e θ, φ Φ 0 0 O Φ 0 C School G. Stefani 39

40 Fixed in space molecules CO C 1s F. Heise et al. School G. Stefani 40

41 Application to sufaces School G. Stefani 41

42 Hole elaxation Global enegy, angula Momentum and paity Enegy, angula momentum, Dipole selections at each step School G. Stefani 4

43 Auge decay e e e E p E A L 3 p 3/ L p 1/ L 1 s K 1s Auge Tansition Double ion valence configuation Multiplet Tems KL 1 L 1 s 0 p 6 1 S 0 KL 1 L,3 s 1 p 5 1 P 1, 3 P 0, 3 P, 3 P 1 KL,3 L,3 s p 4 1 S 0, 3 P 0, 3 P, 1 D EAKL 1 L = EK EL 1 EL, L 1 School G. Stefani 43

44 K Auge spectum K. Siegbahn et al ESCA Applied to fee molecules 0 K I i K II L, L 3 f K III M M i j School G. Stefani 44

45 Zn Auge multiplet splitting L 3 M 45 M 45 Aksela et al. PRL 33, School G. Stefani 45

46 Auge chemical shift School G. Stefani 46

47 Autoionizing decay e e * e E A M,3 L3p 3 p 3/ L p 1/ L 1 s K 1s School G. Stefani 47

48 A Autoionization spectum 3p- 5s, 4f Phys. Rev. A 63,03514 School G. Stefani 48

49 Quantum intefeence What does it happen when the photoemission line concides with the autoionization line? Intefeence between diect and esonant channel Phys. Rev. A 63,03514 School G. Stefani 49

50 Conclusions 1. Valence main lines Popeties of delocalised binding obitals. Inne valence & coe satellites Coelation and elaxation, local electonic stuctue 3. Coe chemical shift Chage state & chemical envionment 4. Angula patten Relative position of neighbouing atoms though diffaction effects 5. Auge Coe hole excitation though e-e inteaction 6. Resonant photoemission Local popeties of valence delocalised states School G. Stefani 50

51 Refeences C.S. Fadley Basic Concepts of X-ay Photoelecton Spectoscopy, in Electon Spectoscopy, theoy, techniques and applications, Bundle and Bake Eds. Pegamon Pess, 1978 Vol. 11, ch.1 available at: S. Hufne Photoelecton Spectoscopy, pinciple and applications Belin Sponge d Edition V. Schmidt Photoionization of atoms using synchoton adiation Repot on Pogess in Physics C.M. Betoni in Synchoton Radiation Fundamental Methodologies and Applications SIF Confeence Poceedings vol 8, pg. 95 C. Maiani in Synchoton Radiation Fundamental Methodologies and Applications SIF Confeence Poceedings vol 8, pg. 11 G. Stefani in Synchoton Radiation Fundamental Methodologies and Applications SIF Confeence Poceedings vol 8, pg. 319 School G. Stefani 51

52 The End School G. Stefani 5