Dear Jaita, in Your case instrumental  response to picosecond excitation is determined by two  connected processes - quick charge of parasitic capacity C of input chains of PMT and slow exponential discharge of the capacity  throw load resistor R of PMT with time RC-1 . If response time  occurs to be more less than emission lifetime  You can observe on oscilloscope screen  lifetime of emission of your substance.

Wish You any success

Jayita,

You can get a pdf file : https://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE-Chapter10.pdf

IRF^2=TTS^2 + Tw^2 + Tj^2

Tw: pulse duration

Ti: jitter in your system

You probably need to read following file:

https://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE-Chapter4.pdf

Peter, the syatem we are using is TCSPC and it is a photon counting method. We use Bh software to take those decay patterns.

Often in these cases you are forced to use a dye that can absorb at your excitation wavelength and emits around your spectral region of interest. Use a quencher like KI to make the dye have a very short lifetime so its emission is like an IRF.

Check out this link: http://www.tcspc.com/doku.php/howto:how_to_measure_the_instrument_response_function_irf

Also see the attached paper for the general procedure

I would suggest maybe the laser dyes Styryl 20 (LC 9940) or Styryl 14 (LC 9450). They are able to absorb around ~530 nm and emit around 930-980 nm. You can check out their specs here:

http://www.chem.ucla.edu/~craigim/pdfmanuals/catalogs/Lamdachrome-laser-dyes.pdf

These dyes may be inappropriate if they are not emitting the IRF in the same spectral region you are planning to do measurements though.

Edit: Those dyes I suggested may not be so good. I re-read your comment and see you are looking at the 1200-1300nm region.

@Sebastian: Thank you for your suggestions. I think it will be helpful for me.

@Peter: It is a MCP-PMT of Hamamatsu R3809U-69