Budó, Ágoston

Ketskeméty, István

English

Budó Ágoston

Ketskeméty István

University of Szeged

FURTHER INVESTIGATIONS ON THE UPPER LIMIT OF FLUORESCENCE YIELD By A. BUDÓ and 1. KETSKEMÉTY Institute of Experimental Physics, József Attila University, Szeged (Received May 2, 1965) According to a formula given in an earlier paper of the authors, the frequency at which the-drop in fluorescence yield begins is completely determined by the position and shape of the emission spectrum. The validity of the formula obtained by a thermodynamical method is confirmed by-results of recent investigations on several solutions. 1. In a former paper [1] the authors investigated the changes in entropy occurr-ing in fluorescence processes and came-to the result that in the case of very small exciting intensities the energy yield rj of fluorescence satisfies the inequality Here v is the frequency of excitation, Avf = l/f(v0) is approximately the half-width of the normalized energy spectrum / (v) of fluorescence, Av denotes the half-width of the exciting band (Av<cAvf), k the Boltzmann constant, T the absolute tem-perature of the solution ; the frequency va is determined by the equation In deriving and applying inequality (1), besides purely mathematical simpli-fications and neglections, the following assumptions of physical character were made: a) A very small quantity of the solution is in contact with a body of great dimensions and good thermal conductivity; its surface is supposed to be black and the part of the exciting energy which is converted into heat is eradiated by this body, b) The spectral intensity of the exciting light as well as that of the fluo-rescence (positive and negative) is small compared to the spectral intensity of the black body radiation of temperature T and it tends to zero in limit, c) It is sup-posed that the inequality (1) obtained for the limiting case remains valid for great intensities of excitation and fluorescence, as long as the intensity of fluorescence is proportional to that of the excitation. As it is to be seen from inequality (1), the drop in yield within the anti-Stokes region begins at frequency v0 and according to (2), this frequency is completely^ determined by the shape and spectral position of the fluorescence spectrum at a. given temperature T. (I> exp(hv0lkT)f(v0)=J v-\xp(hV'/kT)l[f(V')]2dv'. (2> o t a b i c i o 00 No Fluorescent compound and concentration (in mole/liter) Solvent I'e (in 1012 S" ') 4 (in m//) >'o (in 1012 s~ ') 1 Esculin M O " 4 Ethanol 90%, Water 10% 5• 10"3 mole/liter NaOH 712 421 685 2 Al-Morin M O " 3 Ethanol; 2% acetic acid 652 460 614 3 Trypaflavine M O - 4 Ethanol; 2 -10 - 3 mole/liter HCl 634 473 618 4 Aurophosphin M 0 - " . Ethanol 90%, Glycerol 10% 3-10- 3 mole/liter HCl 626 479 614 5 Flavophosphin I -10- 4 , Ethanol 90%, Glycerol 10% 3-10- 3 mole/liter HCl 620 484 611 6 Rhoduline orange J -10- 3 Ethanol; 5-10-? mole/liter HCl 595 504 580 7 Fluorescein M O - 4 Ethanol; 1% NaOH 590 - 509 579 8 Eosin 4 -10- 4 Etanol 80%, Water 20% 5 - 1 0 - 3 mole/liter NaOH 565 531 556 9 . Rose bengale J - JO-3 Ethanol; 5 -10- 3 mole/liter NaOH 537 559 531 10 Rhodamine li MO--1 Ethanol; 3 • 10 - 3 mole/liter HCl 531 . 565 523 FURTHER INVESTIGATIONS ON THE UPPER LIMIT OF FLUORESCENCE YIELD 7 9 10 r _ o _ o — 12 -1 v(in10 5 ) "v 1 \ 1 € \ \ c\ \ lo-O-o' 05 X •o \ I (v) \ Y 1i *> (in 10 s ) v \ 1.01 800 750-© 700 650 700. AM '-o \ I w « r t • ip(v) 0,5 . v f a i o V t , 650 ® '0-G73Xi<\ 600 1M \ v. (in 1o"b') 700 (vi 650 © 600 550 700 •o-o-0" » I . \> \ t (vi \ V oN \ \ \ v ( in i aV) , 0,5 ij(v) 650 600 \ \ \ l(v) -o (in10 6 ) , 700 650 600 650 600 550 500 •10 r ( U'W (z) 0,5h \ V 1,0 0.5 V (in 10 i ) © V (inlo'V) 700 l o r , 650 600 ® 550 650 tfrj 600 . 0 - O - 0 " 600 550 \l(v) 500 0,5 550 \ 1 Iv) 500 \ 0 v (>n10 p ) 600 550 500 <i50 Fig. 1 8 0 A. B U D Ó A N D I. KETSKEMÉTY If the emission spectrum of the solution can be described [2] by f(v) =Nv* ex<p ( —hvUkT) sech [a(v— v„)], (3> the integrand in Eq. (2) is equal to ;VV" sech2 fa(v'— v.)]; thus v0, giving the spectral region of the drop in fluorescence yield, is led back to a and by Eq. (2) because the normalization coeffi-cient N is completely determined by the parameter a and the frequency v. of pure electronic transi-tion at a given temperature. 2. I n o rde r t o c h e c k the val idi ty of inequa l i ty (1), t he ene rgy yields t], s h o w n in Fig. 1 by circles a n d sol id lines, have been d e t e r m i n e d wi th t h e e x p e r i m e n t a l m e t h o d desc r ibed in [3] f o r t he so lu t i ons given in T a b l e I. T h e l imi t ing f u n c t i o n s /(v), ca lcu la ted f r o m the e x p e r i m e n t a l fluorescence spec t r a a n d e q u a l t o t h e exp res -s ion o n the r ight of inequa l i ty (1), a r e s h o w n by d o t t e d l ines in F ig . 1. I n c a l c u l a t -ing /(v), t he va lue of iAvf/Av h a s been t a k e n e q u a l t o 3 a c c o r d i n g to t h e e x p e r i -m e n t a l c o n d i t i o n s . It c a n be seen t h a t t he l im i t a t i on g iven by inequa l i ty (1) is f u l -filled f o r t he so lu t i ons inves t iga ted , emi t t i ng f luo rescence in r a t h e r d i f f e r en t spec-t r a l r eg ions of t h e visible s p e c t r u m . * * * T h e a u t h o r s wish t o express the i r s incere t h a n k s t o d r . J . HEVESI, dr . R . HORVAT a n d dr . L . K O Z M A f o r the i r v a l u a b l e p a r t i c i p a t i o n in t h e inves t iga t ions . References [1] Budó, A., 1. Ketskeméty: Acta Phys. Polonica, 26, 385 (1964). |2] Dombi, J., I. Ketskeméty, L. Kozma: Acta Phys. et Chem. Szeged, 10, 15 (1964). |3] Ketskeméty, I., J. Dombi, J. Hevesi, R. Horvai, L. Kozma: Acta Phys. et Chem. Szeged, 7,. 88 (1961). О ВЫСШЕЙ Г Р А Н И Ц Е ВЫХОДА Ф Л У О Р Е С Ц И Р У Ю Щ И Х РАСТВОРОВ А. Будо и И. Кечкемети То частота, у которой начинается падение выхода флуоресценции, по заданной формуле в одной предыдущей работе авторов, с положением и формой спектра флуорес-ценции практически полностью определена.. По термодинамическим путем полученную формулу, результаты новых экспериментальных исследований в случае многих раство-ров, подтверждают. 

Further investigations on the upper limit of fluorescence yield

http://acta.bibl.u-szeged.hu/23662/1/phys_chem_011_fasc_003_004_077-080.pdf

Further investigations on the upper limit of fluorescence yield

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