INVESTIGATION OF THE OSL SIGNAL FROM VERY DEEP TRAPS IN NATURAL QUARTZ

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1 Meiterrnen Arheology n Arheometry, Vol. 010, No., pp Copyright 010 MAA Printe in Greee. All rights reserve. INVESTIGATION OF THE SIGNAL FROM VERY DEEP TRAPS IN NATURAL QUARTZ G. Kitis 1, N.G. Kiyk, G.S. Polymeris, n V. Pgonis 1 Aristotle University of Thessloniki, Nuler Physis Lortory, Thessloniki, Greee ISIK University, Physis Deprtment, Fulty of Siene n Arts, 980 Sile, Istnul, Turkey Culturl n Eutionl Tehnology Institute R.C. Athen/Arheometry Lortory, Xnthi, Greee MDniel College, Physis Dept, Westminster, MD 11, USA Corresponing uthor: gkitis@uth.gr ABSTRACT It hs een reently reporte y severl stuies tht thermlly trnsferre optilly stimulte luminesene (TT ) signl from qurtz grins n e use to exten the ting rnge for qurtz smples. The TT signls re elieve to onsist of reuperte (Re) omponent n si trnsferre (BT ) omponent. In the present work the TT signls from severl types of unfire qurtz smples were stuie. A speil protool ws use, whih llowe the mesure the from very eep trps (VDT) s funtion of the stimultion temperture. It ws foun tht ll qurtz smples exhiit TT signls, whih re epene on smple n on the stimultion temperture. The tivtion energy of the proess ws evlute n the influenes of the TT on the Re ting protool re isusse. KEYWORDS: qurtz, eep trps, TT

2 9 G. KITIS et l INTRODUCTION Severl reent stuies hve shown tht thermlly trnsferre (TT ) signl from qurtz grins n exten the ting rnge for qurtz smples of vrious origins y lmost n orer of mgnitue (Wng et l., 00; Wng et l., 00; Tsukmoto et l., 008). It hs een suggeste tht the TT signl omprises reuperte (Re) omponent n si trnsferre (BT ) omponent, Aitken (1998). Dting protools se on the TT signl ttempt to seprte the BT signl n the Re signl, y therml tretments. It is suggeste tht the Re signl is the mjor ontriutor to the TT signl. BT signl is smller ut signifint omponent. Aitken (1998) suggeste tht the Re results from oule trnsfer proess while the BT ws ue to eletrons 10 SLE ME Stimultion time (se) trppe originlly in light insensitive trps. An lterntive single trnsfer proess for the proution of Re hs een suggeste y Amie et l. (008) n ws moele y Pgonis et l. (008). In the single trnsfer proess, light sensitive trp ts s the soure of eletrons for the Re. It is prole tht the BT signl, or t lest some prt of it, origintes from Very Deep Trps (VDT). As VDT we onsier those trps whih re responsile for TL glow peks with pek mximum temperture of 00 0 C. The im of the present work is to investigte the ontriutions of the signls from the VDT in unfire nturl qurtz of vrious origins, to set protools involving mesurements t high tempertures like Re ting protool ME Stimultion time (se) Figure 1: High effiieny TT urve shpes for qurtz mesure t vrious stimultion tempertures. Curve () C, Curve () 0 0 C n Curve () t 0 C. Curve () orrespons to the kgroun signl mesure t room temperture. MATERIALS AND APPARATUS The smples were qurtz of vrious origins n from iverse lotions of Turkey. Smples with lortory oes SLE n were very young ostl unes ner Istnul, with Gy n Gy equivlent oses (Kiyk n Cnel, 00).Smple ws lso from young otl unes from Inkumu Brtin, in the mile prt of the Blk Se Region with nturl ose 0.0 Gy. Smple PTR ws eposit from Ptr in the Meiterrnen ost n ontin nturl ose out. Gy. Smples SRZ1 n SRZ were from ifferent lyers of mrine terre in Sroz, on the Egen ostl re. These smples re ol n the nturl SAR p

3 INVESTIGATION OF THE SIGNAL FROM VERY DEEP TRAPS IN NATURAL QUARTZ 9 leoose ose in qurtz grins were estimte s 181 n 19 Gy respetively. ME1 n ME were from fluvil terre seiments from n re lose to the Mrmr Ereglisi, in Europen prt of the Mrmr Region with 1 n 1 Gy pleooses.. The smples s reeive were wet sieve, n qurtz grins with imensions etween 90 n 180 μm were selete n eposite on stinless steel isks of 1 m re. Qurtz purity of the smples ws previously verifie y IRSL mesurements t mient temperture. Blue light emitting ioes (LEDs) (0 nm, 0 mw/m ) were use for stimultion intensities linerly inrese etween 0 n mw/m. All mesurements were performe using the RISØ TL/ reer (moel TL/ DA 1) equippe with out 0.1 Gy/s 90 Sr/Y β ry soure. The reer is fitte with n EMI 9QA PM Tue. Luminesene signls were etete through U 0 filters. The TL reout PTR heting rte use ws 1 K/s for ll mesurements. EXPERIMENTAL RESULTS AND DIS CUSSION The multi liquot protool use to stuy the effiieny of TT from VDT ws the following: Step 1: Nturl smple+00gy et ose. Step : TL reout to 00 0 C. Step : Test ose (TD= 10 Gy) n TL to 00 0 C. Step : Blue CW t vrile stimultion temperture Ti (1C C in steps of C) for 000 s. Step : Resiul TL up to 00 0 C. Step : TD n TL to 00 0 C. Step : Repet steps 1 for new smple n new stimultion temperture Ti SRZ Stimultion time (se) 10 SRZ Stimultion time (se) Figure : Low effiieny TT lue urve shpes for qurtz mesure t vrious mesuring tempertures. Curve () C, Curve () 0 0 C n Curve () t 0 C. Curve () orrespons to the kgroun signl mesure t room temperture Sine the egree of filling of VDT y the geologil ose in not known, n itionl irrition is given in step 1 to ensure the filling of the VDT. In step, ny trpping level responsile for TL glow peks up to 00 0 C is erse. The mesurement in step is use to evlute the sensitivity to low test ose n verify tht the heting up to 00 0 C erses the TL signl

4 9 G. KITIS et l ove 00 0 C own to the kgroun level. Step ims to stuy the mgnitue of the TT signl from VDT s funtion of the stimultion temperture. Step is pplie to fin whether TL signl ppers etween C fter the stimultion t high tempertures, ue, for exmple, to phototrnsfer proess. Finlly step will evlute the sensitivity to the low test ose s in step n llows to evlute how the pplie protool ffets the sensitivity of the qurtz smple. The protool ws pplie to the speifi eight ifferent qurtz smples esrie ove. In six of these smples only three mesuring tempertures were use (190, 0 n 0 C). On the other hn, sine the mesurement t high tempertures is thermlly tivte optil stimultion proess, two smples were selete, one with high n nother with low TT signls. In these two smples the optil stimultion ws stuie in the whole temperture region from 1 to 0 C in steps of 0 C. The purpose of this experiment is to evlute the tivtion energy vlues of the thermlly tivte optilly stimulte proess. The min result of this experiment respons iretly to the first question set in the present work, nmely to show tht ll qurtz smples exhiit TT signls. The intensity of the signls from VDT ws foun to epen on the type of qurtz smple use. The TT urves from VDT re shown in Figs. 1 n. In Fig. 1 the smples hving very high effiieny for TT re presente wheres Fig. shows the smples hving low TT effiieny. In ll ses the kgroun level is inlue. It is useful here to present in Fig. the results of the steps 1,,, n of the protool. The glow urve () of Fig. results fter the irrition with 00 Gy. The glow urve () reeive in step gives (i) the sensitivity to low ose fter the hevy irrition in step 1 n ssures (ii) the TL reout in step erses the TL ove 00 o C to the usul kgroun level n it oes not leves ny intense resiul TL signl t the very high tempertures. The sene of ny signl in urve () of step, shows tht the optil stimultion t the high tempertures of step oes not use ny re trpping to the low temperture glow peks. Finlly, the glow urve (), whih lmost oinies with glow urve () shows tht the smple tretment in steps to oes not influene the sensitivity of the smples. TL(.u.) , Temperture ( 0 C) Figure : ) NTL plus 00 Gy et ose. () TL glowurve from step. () Resiul TL fter lue CW stimultion t the temperture of o C () TL from step. The si hrteristi of TT urve is tht the TT signl inreses from zero to higher level n then tkes the form of more or less stle emission. However, in some smples for very short stimultion times fst omponent ppers. These ses re shown in Fig., where only the first 00 s of the stimultion urves re inlue in the plot. Furthermore, it ppers only for stimultion tempertures lower thn 1 0 C, n not for higher stimultion tempertures. Oviously this omponent n not e relte to the known fst omponent originting from the eletron trp responsile for the 0 C TL glow pek of qurtz, sine this eletron trp ws emptie y the TL reout up to 00 0 C. Fig. shows the ehvior of the totl TT s funtion of the stimultion temperture. The exponentil nture of the ehvior llows the evlution of the tivtion energy of the optil stimultion t high tempertures for two of the smples. The respetive Arrhenius plots re shown in Fig.. In the se of qurtz smple whih exhiits strong TT signl, the tivtion energy ws foun to e E=0.±0.0 ev, wheres for the se of qurtz, whih shows wek TT signl, it ws foun to e E=0.±0.0 ev 0 TL (.u)

5 INVESTIGATION OF THE SIGNAL FROM VERY DEEP TRAPS IN NATURAL QUARTZ Stimultion time (s) Figure : Exmples of TT urves showing fst omponent t very short stimultion times. Curve () qurtz, urve () PTR qurtz, urve () SLE qurtz n urve () the kgroun. Sine the therml quenhing effet is often reporte in qurtz, it is neessry to exmine the results of Fig. uner the influene of therml quenhing. Assuming tht the therml quenhing prmeters C=.8 x10 n W=0. ev, given y Wintle (19) s representtive for qurtz, it is possile to orret the intensities ue to therml quenhing s follows. Initilly, the vlues of the therml quenhing effiieny were evlute for eh one of the stimultion tempertures. Then the intensity t eh temperture is orrete ue to therml quenhing y iviing it with the evlute orresponing therml quenhing effiieny. Then the logrithm of the orrete vlues is plotte ginst 1/kT (Arrhenius plots). The results for oth integrte regions re shown in Fig.. The resulting vlues of the tivtion energies were foun to e E=1.0±0.0 ev, n E=0.9±0.0 ev for n. Using only the present t, it is not possile to eie whih vlues re the orret ones. Therefore, seprte experiments of TL s funtion of heting rte re require in orer to investigte if the therml quenhing effet is present or not in the speifi qurtz smples stuie.. CONCLUSIONS Uner the omine tion of therml tivtion n optil stimultion eletrons trppe t VDT re lierte to the onution n n reomine emitting photons. This is known s TT signl. Eight unfire qurtz smples of vrious origins tht were stuie, exhiite TT signls in wie region of stimultion tempertures. It ws foun tht the TT signl epens strongly on the type of qurtz smple stuie. This TT signl oul e n ppreile omponent of the BT signl involve in the TT ting protools. Aoring to the results of the present work, the importne of the BT prt of the TT ting protool epens lso on the smple stuie, n we reommen tht the BT signls re inlue in TT protools, rther thn eing omitte. (.u.) () 1E E E T ( 0 C) ln() , E=0. ±0.0, E=0. ±0.0 () / k T Figure : Arrhenius plot showing the tivtion energy evlution for the TT signl without tking into ount therml quenhing. qurtz E=0.±0.0 ev n qurtz E=0.±0.0 ev

6 98 G. KITIS et l (.u.) () E8 E8 1E8 0E0 ln() , E = 1.0 +/- 0.,0, E = 0.9 +/- 0.0 () T ( 0 C) / k T Figure : Arrhenius plot showing the tivtion energy evlution for the TT signl tking into ount therml quenhing. qurtz E=1.0±0.0 ev n qurtz E=0.9 ±0.0 ev REFERENCES Amie, G.A., Biley, R.M., Wng, X.L., Wintle, A.G., 008. The mehnism of thermllytrnsferre optilly stimulte luminesene. J. Phys. D: Appl. Phys. 1, 10. Aitken, M.J., An Introution to Optil Dting. Oxfor University Press, Oxfor. Bulur, E., 000. A simple trnsformtion for onverting CW urves to LM urves. Rit. Mes., Kitis, G. An Pgonis, V Computerize urve eonvolution nlysis for LM. Rit. Mesur., 1. Kiyk, N.G., Cnel, T., 00. Equivlent ose in qurtz from young smples using the SAR protool n the effet of prehet temperture. Rit. Mes. 1, Pgonis, V., Wintle, A.G., Chen, R., Wng, X.L., 008. A theoretil moel for new ting protool for qurtz se on thermlly trnsferre (TT ). Rit. Mes., Tsukmoto, S., Duller, G.A.T., Wintle, A.G., 008. Chrteristis of thermlly trnsferre optilly stimulte luminesene (TT ) in qurtz n its potentil for ting seiments. Rit. Mes., Wng, X.L., Lu, Y.C., Wintle, A.G., 00. Reuperte ting of fine grine qurtz in Chinese loess. Qut. Geohronol. 1, Wng, X.L., Wintle, A.G., Lu, Y.C., 00. Thermlly trnsferre luminesene in fine grine qurtz from Chinese loess: si oservtions. Rit. Mes. 1, 9 8. Wng, X.L., Wintle, A.G., Lu, Y.C., 00. Testing single liquot protool for reuperte ting. Rit. Mes.,