There are different methods to measure radiative and nonradiative rates

Method 1: Measure lifetime (Tau, reciprocal of sum of all radiative rate and nonradiative rate processes) and take its reciprocal to give you a numerical value (lets call it A). Lifetime can be measured using the method given below.

Measure radiative rate of a fluorophore under the given experimental conditions (like solvent, temperature etc) using one of the methods given below, to give you a numerical value (lets call it B).

Then non-radiative rate can be calculated by subtracting B from A i.e. A-B

This can be represented as

Tau = 1/(kr+Knr)

(1/Tau) - Kr = Knr

Tau - fluorescent lifetime

kr - radiative rate

knr - nonradiative rate

Methods to estimate Radiative Rate of a fluorophore under the given experimental conditions

1) Estimate radiative rate experimentally as given in this paper V. V. N. Ravi Kishore et al., Phy. Chem. Chem. Phys., Vol-5, 2003, 1386-1391. or

2) Measure radiative rate by dividing the experimentally measured quantum yield of a fluorescent dye with its experimentally measured lifetime or

3) Theoretically estimate radiative rate using Strickler Berg equation from the absorption and emission spectra of the fluorophore. (Ref: Strickler and Berg, J. Chem. Phys. Vol 37, 1962, Pg 814).

Method to measure fluorescent lifetime experimentally using a nanosecond laser

Select a fluorescent dye, then using a nanosecond laser, monochromator, fast detector and oscilloscope one can measure lifetime. If the fluorescent dye has a long lifetime and single exponential decay then things are easy and simple. If not, then things get complicated and you need to worry about lot of other things. one of them being deconvolution.

Lifetimes can also be measured using any of the commercially available instruments. 

Method 2: Nonradiative rates also be measured using other methods like photoacoustic spectroscopy.

In certain dyes of structural rigidity, one can safely say that there are direct mechanism of losses via non-radiative transitions, and that the other channel for de - excitation is fluorescence. Measuring the losses, you can determine with enough precision for most applications, the fluorescence efficiency.

The method for non-radiative losses determination is to perform a laser photoacoustic analysis with a laser that covers the range of emission of the dye. You may find lots of bibliography on that. For example: Silvia Braslavsky, Gabriel M Bilmes, Jorge O Tocho, myself, Mayo Villagrán Muniz, etc.

In cyanines it is interesting that you can determine another channel of loss: photoisomerization. In this case, see Bilmes papers on that subject.

Hope it was helpful.

Not sure if you are looking for the setup . If so you can use a fast photodiode along with a  monochrometer to measure the decay . The choice of the photodiode would depend on the decay rates of the transitions you wish to observe

One method is  by  measuring fluorescent lifetimes of the dye molecule in different solvents( polar  or nonpolar) and also with variations in pH . You need a streak camera ( Hamamatsu)  for measuring fluorescent lifetime in approx 100 femtoseconds resolution.

dear Venkatesh I am afraid there is no very simple way to get these information. If you stick on using the nanosecond laser, first of all you need to know if the decay rate of your dye is reasonably longer than the laser pulsewidth. If this condition is not satisfied you will always observe a convolution of the two times. The detection setup also depends on the decay rate you want to observe: if it is in the few ns range you need a special electronics as TCSPC. If the decay rate is around tens of ns, maybe you can simply use a fast (i.e. small)  photodiode. To obtain the non-radiative rate using this setup you need to change some parameter influencing this rate, as the temperature with a criostat. Measuring the lifetime as function of temperature you can disentangle the radiative and non-radiative rates.

On the other hand you could obtain the informaton on non-raidative rate also measuring the absolute fluorescence quantum yield with a fluorimeter equipped with the dedicated attachement (integrating sphere). While this method is also somewhat delicated it may be easier to implement, if you do not have a criostat.. I hope these very general considerations can help.

(1). Excitation with a laser pulse of 10 ns, detecting the fluorescence by a fast detector (IP28-PMT (Roorkee) with a fast dyanode chain, or any fast detector) and feeding this signal to a 100 MHz oscilloscope (1/100 MHz= 10 ns) , one can just measure the decay time of about 10 ns with certain accuracy.  Accordingly the parameters change for the required decay.  changes of techniques (TCSPC, Streak camera with fs oscillator, flash lamp, ps laser)  are expensive by several order of magnitude. 

(2). For calculation of the lifetime from the absorption and fluorescence  measurements, you can refer to S.J. Strickler, R.A. Berg, J. Chem. Phys. 37 (1962) 814.

Best wishes, Prem

There are different methods to measure radiative and nonradiative rates

Method 1: Measure lifetime (Tau, reciprocal of sum of all radiative rate and nonradiative rate processes) and take its reciprocal to give you a numerical value (lets call it A). Lifetime can be measured using the method given below.

Measure radiative rate of a fluorophore under the given experimental conditions (like solvent, temperature etc) using one of the methods given below, to give you a numerical value (lets call it B).

Then non-radiative rate can be calculated by subtracting B from A i.e. A-B

This can be represented as

Tau = 1/(kr+Knr)

(1/Tau) - Kr = Knr

Tau - fluorescent lifetime

kr - radiative rate

knr - nonradiative rate

Methods to estimate Radiative Rate of a fluorophore under the given experimental conditions

1) Estimate radiative rate experimentally as given in this paper V. V. N. Ravi Kishore et al., Phy. Chem. Chem. Phys., Vol-5, 2003, 1386-1391. or

2) Measure radiative rate by dividing the experimentally measured quantum yield of a fluorescent dye with its experimentally measured lifetime or

3) Theoretically estimate radiative rate using Strickler Berg equation from the absorption and emission spectra of the fluorophore. (Ref: Strickler and Berg, J. Chem. Phys. Vol 37, 1962, Pg 814).

Method to measure fluorescent lifetime experimentally using a nanosecond laser

Select a fluorescent dye, then using a nanosecond laser, monochromator, fast detector and oscilloscope one can measure lifetime. If the fluorescent dye has a long lifetime and single exponential decay then things are easy and simple. If not, then things get complicated and you need to worry about lot of other things. one of them being deconvolution.

Lifetimes can also be measured using any of the commercially available instruments. 

Method 2: Nonradiative rates also be measured using other methods like photoacoustic spectroscopy.

http://www.uni-leipzig.de/~physik/tl_files/mona/pdf/Photonik%202/Paper/Single%20Molecule/JChemPhys_37_814.pdf

This is the original Strickler-Berg publication and still better than textbooks

The question is confusing! What you mean by "fluorescence decay rate (radiative and non-radiative)"? Is it the measurable decay rate of the fluorescence K1=1/t1 (t1 is the lifetime of S1 state)? Or you want separately the radiative Kr and the non-radiative Knr decay rates of S1? Mauro Falconiery has right; measuring the fluorescence lifetime t1 (S1 decay rate, respectively) is simple in case it is reasonably longer than the resolution of your time-resolved fluorescence measuring device. By contrasts, in general, there is not a direct & simple way to measure separately Kr and Knr, but rather to evaluate them from indirect measurements. For example, measuring the absolute value of the fluorescence quantum yield Qf will provide you some idea as well as comparison of S1 with a theoretical estimate of Kr.

Dimitar

What do you mean with your last words "comparison of S1... with Kr"

an energy state versus a radiative rate?

Thank you Harry, I apologize. I means "comparison of K1 with... Kr".

Dimitar

The questioner specifies in the sentence below the actual question in bold letters:

"How can I find out radiative and non-radiative decay rates"

(kr can be calculated / estimated by the Strickler Berg approach) 

you can also measure from quantum yield and life time data.

The total decay rate can be determined form the condcutivity decay rate and the radiative decay rate can be determined from the total photoluminescence decay rate. The nonradiative rate is the difference between the total and the radiative one.