Lifetime Measurement Techniques
6.1.2. Pulse Method
Our goal is to measure the luminescent lifetime and to determine air pressure through the Stern-Volmer relation. A variety of methods can be used to extract the lifetime from the luminescent response to a time-varying excitation light. The pulse method is the most direct method widely used in photochemistry (Lakowicz
1991, 1999). After PSP is excited by a pulsed illumination light, the luminescent decay is measured using a fast-responding photodetector and acquired using a PC or an oscilloscope. The lifetime is calculated by fitting the time-resolved data with a single exponential function or a multiple-exponential function. This direct time-domain approach was used by Davies et al. (1995) for lifetime measurements of PSP. For certain PSP with multiple distinct lifetimes, the pulse method allows simultaneous determination of pressure and temperature if the lifetimes have sufficiently different Stern-Volmer coefficients as a function of temperature. In this case, given the lifetimes (xi), a system of equations for pressure and temperature are
= Ai(T) + Bi(T)—!—, (i = 1,2, ••• N, N > 2 ) (6.13)
In principle, unknown pressure and temperature can be simultaneously determined by solving Eq. (6.13).