Theory of the Stern--Volmer coefficient for dense fluids

Journal Article · Mon Jun 15 04:00:00 EDT 1981 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.441088· OSTI ID:6498680

Baird, J K; McCaskill, J S; March, N H

In phenomenological theories of fluorescence quenching in dense fluids, one assumes that the Stern--Volmer coefficient K has a dependence upon a limited number of parameters. Denoting by K/sup 0/ the value of K when the quencher molecules are infinitely dilute, our starting point is that K/sup 0/ = K/sup 0/(D,t,k,R), where D is the sum of the diffusion coefficients of the fluorophore and quencher, k is a rate constant, t is the unquenched lifetime of the fluorophore, and R is the range of interaction between fluorophore and quencher. We then find by dimensional analysis that K/sup 0/ can be simplified to K/sup 0/ = DRtxF (k/DR,Dt/R/sup 2/), where F(x,y) is a function of just two variables. Furthermore, if S is a function specifying the region of configuration space in which fluorophores and quenchers interact (G. Wilemski and M. Fixman, J. Chem. Phys. 58, 4009 (1973)), we find that K/sup 0/ depends only upon an average of S over the steady state fluorophore--quencher pair correlation function. Under ordinary conditions, k/DR and Dt/R/sup 2/ will be large. We note that in this limit K/sup 0/ approaches the Smoluchowski value 4rDRt. Correction terms to the Smoluchowski value are explicitly computed, however, when S is a delta function or a step function. Inasmuch as both forms lead to corrections tending in the same direction, it may be difficult to distinguish them by experiment. Thus, we conclude that future theoretical work should focus on a more realistic form for S.

• Research Organization: Health and Safety Research Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
• OSTI ID: 6498680
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 74:12; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640420* -- Fluid Physics-- Properties & Structure of Fluids-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CORRELATION FUNCTIONS
DE-EXCITATION
DENSITY
DIFFUSION
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
FLUIDS
FLUORESCENCE
FUNCTIONS
LIQUIDS
LUMINESCENCE
PHYSICAL PROPERTIES
RADIATIONLESS DECAY