Quantum Efficiency Measurements Using a 2π-Geometry Elliptic Mirror

M e th ods of abso lut e a nd re lati ve radi a nl a nd q ua ntum effi c ie ncy m eas ure me nts a re described fo r ultrav iole t , vis ibl e , ca thod e-ray, a nd x·ray exc ita tio ns. Da ta o n so me s ta nd a rd lumin esce nt ma te ri a ls a re gjve n.Key word s: Ca th ode· ray exc itation ; lum inesce/lce; lumin esce nce st a n da rd s; phosp ho rs; qu a ntum e fficie ncies; ra di a nt efficie nc ies; UV exc it a ti on; ,· ray exc it a tio n. . IntroductionMe th ods of absolut e radi a nt a nd qu a ntum e ffi cie ncy meas ure me nts are giv e n togeth e r with meth ods of relati ve e ffi c ie ncy meas ure me nts. Th e me th ods are es pec ia ll y s uit ab le fo r powd e r ma te ri als fo r whi c h th e a ngular di s tributi on of th e e mitted lumin esce nt radi ati on is La mbe rti an.Th e re la ti ve meas ure me nts a re perfo rm ed with th e aid of s ta nd a rd ph os ph ors, whose effi cie ncies have previously bee n de te rmin ed by a bsolute meas ure me nts. Methods are give n fo r excita ti on of th e ph os phors by ultraviole t a nd vis ible radiati on , cathod e rays and x rays.F or samples with non-La mbe rti a n e mi ss io n di stributio ns, a me thod is desc ribed in whi c h a n Ulbri c ht 's s phere or an e lliptical mirror is used. . Ultraviolet ExcitationAll powder phosphors are meas ured us in g a thi c k layer (thi c kn ess ab out 2 mm) at th e irradi ated side. Th e detection tak es place pe rpe ndi c ular to th e plan e of the phos phor, t he excitati on is at a n a ngle of 50° with th at plan e (see fi g. 1). Th e e xcita tio n wa vele ngth ( A exc) or regio ns a re iso la ted from a hi gh pressure merc ury la mp by inte rfe re nce filt ers, the arc being foc used on th e phos phor with a qu artz le ns. In thi s way a hi gh excita ti on de nsity is reached , but generally well below th e excitation region where s aturation e ffects s ta rt. This is es peciall y ad vantageo us wh en a rela ti vely in se ns iti ve th erm oele me nt is used as a d etector.* P aper p re se nt ed at th e W ork s hup Sem in a r 'Slandard izat ion in S pec trophutometry a nd L u m in esce lwe Meas ure rn e nl s' held a t the Nat iona l Burea u uf Standards. Ga ithersbu rg , Md .. Nove mbe r 19

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“…The use of a 2 π -geometry elliptical mirror [ 21 ] instead of an Ulbricht’s sphere gave nearly the same results.…”

Section: Measurements Of Light-emitting Diodes Crystals Etcmentioning

confidence: 78%

Some methods of luminescence efficiency measurements

Bril

Jager‐Veenis

1976

J. RES. NATL. BUR. STAN. SECT. A.

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“…2 nm). We measured the quantum efficiency with a set-up according to van der Does-de Bije [5] using CaWO, as a standard. The methods used for the determination of the decay times have been reported in [6].…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…The absorption coefficient versus photon energy thus obtained is depicted in Fig. 6 (5) in which o,, is a constant and hw the effective phonon energy; a,, hv,, and values of u were determined from Fig. 6.…”

Section: Pbmoomentioning

confidence: 99%

See 1 more Smart Citation

Luminescence of Lead Molybdate and Lead Tungstate. I. Experimental

Loo

1975

Phys. Stat. Sol. (a)

188

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Optical properties of single crystals of lead molybdate and lead tungstate (scheelite structure) have been investigated in order to identify the nature of the luminescent centres. Absorption, emission, and excitation spectra at different temperatures (1.5 to 300 K) and photoconductivity and quantum efficiency measurements at 77 K are reported. The greenyellow emission of both compounds is probably due to a centre being very much alike in PbMoO4 and PbWO4. The blue emission of PbWO4 is ascribed to the tungstate group as in the alkaline‐earth tungstates.

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“…Peters in an open tube GaP-HCI transport system (6). However Dyakonov (5) observed the expected extrinsic behavior in a closed-tube system, which lends itself more to equilibrium conditions than does an open system.…”

Section: Resultsmentioning

confidence: 99%