Playing billiards with electrons: double photoionisation with a single photon

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p>Aa single photo can -direcly oionie only oneh electros ofan atom. Aa smultaneous ejrectios ofa "e codh electro, i.e.: double photoionisatio0, my oc cu only iof the electronn wit in theatom -intetact with eacho thr. If boith electron are ejrecped_frmn theK-eshll,fa "o-c alpedhollrowatom -sy fomed, wthre in theK eshll -syempty wtiblehHigexteshlln are popuplatd (<"spnv class=HLiontexhreF">Fgure 5). Hllrowatomn are ofa gbret -inteest -i, mny fields, rangying_frmnatomficphysicsg tosurfance scienc. Whrehdeclaying yfa 1s 2  heligh= 1s 12p 1y tranictios(un,exlinyingdenoitsdholse slate)n thyyemitfa Kh  heligh=1,2 hypserlatilltle photo <"spnv class=HLiontexhreF"[1]. Thus, double photoionisationaodh electro- electros-intetactionscan bse studidg yfhHig- resolutionX-rmy hypserlatilltlesplecta measureumens. tnabl "borde="0y" tilpaddiang=0y" til"spaiang=2" "width"100%S"> Fgure5o.jpg "width"485" /> >Fg. 5: Schermatcd r/prementatios of theprocessesy fo a)a single photoionisationaodhb): double photoionisatio0,wthre wavyfar"rosgdenoite photos, and ctarightar"ros,h electrosmoation. The finale slats of thehypserlatilltleemisstionprocess -syleftn with a plecratodhols0,wtirch sylmate fialped yfano thrh electroscbretying covientonalediagramnX-rmy emisstionmlins. /tnabld> p>  p>Usying beamlins <"ctrog>ID16 ( ESR) andX25 (NSLS, USA) whehavse studidg double photoionisationnlea ihtsgeneogy hrshold, E<"spnv class=up" /sb>thh, i 3dy tranictiosFgure 6 ecomp ref the covientonaleCueK<"spnv class=up"  heligh=1,2 diagramnsplectum ofa 1s 1  heligh= 2p 1y tranictios withihtshypserlatilltlecouinte-par. The I(K<"spnv class=up"  heligh=1)/I(K<"spnv class=up"  heligh=2) = 2s-intanicy oratid rfelecef thenumbhrhoratid of theL<"spnv class=up" /sb>III andL<"spnv class=up" /sb>II electron. >Forhypserlatilltls,h themeasuredhoratid syvascly differren,h eyingdentemlined yfs electiosrdulehorathrhthan byf theL<"spnv class=up" /sb>III/L<"spnv class=up" /sb>II electroenumbhrhorati. The <"spnv class=up" em>Kh  heligh=1 mlinerecquirsy lippming he eshll-changying2p electro’snspin0,wtirch sy fobhidde in theLS couplyingdComietyinglro-Zwatomn. Iin therangts ofZ estudidgthre surch lippming sy-parly allroed, andthe <"spnv class=up" em>Kh  heligh=1 mlinehan a nro-zeros-intanicy. tnabl "borde="0y" tilpaddiang=0y" til"spaiang=2" "width"100%S"> Fgure6o.jpg "width"472" /> >Fg. 6: a)aTthe covientonaleCueK  heligh=1,2 diagramnsplectum.hb):TthehypserlatilltleCueK /su>h< heligh=1,2 splectum.hNoitethe differrece in therelmaives-intaniciges of thetwo emisstionmlins in thetwo splect<"spnv class=Sstyl4">a /tnabld> pv class=up" /spnv class=HLiontexhreF">Fgure 7 (inset)a hrosgmeasuredhR=I( em>Kh  heligh=1,2)/I(K< heligh=1,2) -intanicy oratisyvn. oioniming photo geneog. Thist is thefirst systermatcdmeasureumens of thenlea- hrsholdh ehaviocu oofR fo aerangts of elumens.:Ttheveryglringrlauoratioerangt, ~70% oofE<"sb>thh, slndsd ou im mediatip. E<"sb>th andthe rlauoratioerangtns and valus in theinset differ amoing he elumens.:Never heules0,wthon salped yf he bindian geneoiges of theindiirecly-oioniedeK- electron aandthe rlauoratioe valus (wtirch, icidmentlly, are fouidg todecbrese an ~Z–1.6) a -inrFguian univeerllh ehaviocu isrevealpe:n allcurvus /collpie on to a singlecurvu (<"spnv class=HLiontexhreF">Fgure 7). tnabl "borde="0y" tilpaddiang=0y" til"spaiang=2" "width"100%S"> Fgure7o.jpg "width"446t"/> >Fg. 7: Relmaives double photoionisationprobabilicy R fo various eelumens an a funectios of he xcess photo geneog abovey hrshold, E-E<"sb>th,n salped yf he bindian geneoys of he "e codatr oioniede electro, E<"sb>th-E<"sb>K0,wthre E<"sb>Kt is thebindian geneoys of he diirecly-oioniedeprimatr electro.:Ttheinset hrosg theraw cross-srectiosy fo eacheelumen.:Tthesolidecurvu is the( salpe)n thoreatcllhKOeprmedectios<"spnv class=HLiontexhreF"[2]. /tnabld> p>Hows dref the double photoionisationoc cu? >For photoss of eneoigesE >> <"spnv class=up" em>E<"sb>th,h theoioniede electro -syejrecped with averyghHig klinatcdgeneoy, changyingabruprly theatomficpontenillhtactingoin theo thrh electros.:Tthe"e codatr electro /finshihtelfh in an ecicped slat, andhan a f inienprobabilicy of eyingejrecpe. Thist is theshake-offt(SO) model0,wtirc, hroever,t isin.valiv couse o <"spnv class=up" em>E<"sb>th,hwthre theoioniming photo’sngeneoys isjust barely enouig o overcomes thebindian geneoys of he electro.:Ofn theo thrh thoreatcllhmodels only th knloc- out(KO) models<"spnv class=HLiontexhreF"[2] agregeswhll (balu mlineios<"spnv class=HLiontexhreF">Fgure 7 andmlins in theinset)a with themeasuredhuniveerllhevsolutionoofR nlea hrshold, wthre theejrecped phot electro -syslrowaand caysglrinhrh wit in thebouides of theatom. Iin theKOemodels the double photoionisationproceedes yf he diirecly-oioniede electro knloctingoutf he "e codatr ont, s in billiard,goinihtswmy oun.:Moreover,t theKOeprocess auonsd ou o bhea quasi- clastcll,horathrhthan a quantum, effecth, i spiats ofihtsoc currece wit in thesanecumnsanecotum of thequantumsregime:n theineneebouides of theatom. Thus, double photoionisationseemsg toevsovu _frmna quasi- clastclleKOe billiardsprocess nlea hrshold to afullyequantumsSO effecte athHig oioniming photo geneoies. p>Iin coclustio0,whehavsedentemlined double photoionisationprobabiliciges yfmeasurming he evsolutionoof thehypserlatilltlesplectum _frmn the hrshold upwiards fo elumens 23  heligh= Z  heligh= 30. We suggest tWhatnlea he hrshold he xcintatiosisna quasi- clastclleKOeeffecteorathrhthan a quantumfmechantclleSO ont, anddemoi ctathea univeerllh salyinglaw fo the double photoionisationgeneoysevsolutionnlea hrshold. p>  pv class=HLhrestim">P icipllhpPublicatio andauthtors pv class=HLhres">S. Huotari (a), K. Hämälälinn (b), R. Diamant (c), R. Shatro (c), C.C. Kao (d), andM. Deutstch c), Phys.:Rev. Lett. <"ctrog>101, 043001 (/200).
em>(a)e ESRFbr "/>(b) Di/visionoofMmaterias Physics, De-parumens ofPhysics, Univeericy ofHelsinki (Finl an)Fbr "/>(c)fPhysics De-parumen, Bar-Il a Univeericy (Israel)Fbr "/>(e)nNantonale>SynchrotronLrightSsourc, BrookhavsnnNantonaleLlaboraotr (USA)
pv class=HLhrestim"Referrecers pv class=HLhres">[1] R. Diamant, S. Huotari, K. Hämälälinn, R. Shatro, C.C. Kao, andM. Deutstc, Phys.:Rev. Lett. <"ctrog>91, 193001 (/203).
[2] T. Schnew,ext andJ.M. Rost, Phys.:Rev. A <"ctrog>67, 062704 (/203).<
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