Nature and Kinetics of Non-Stationary Light Absorption Induced by Femtosecond Laser Pulses in Lead Phthalocyanine and Chloro-Aluminum-Chloro-Phthalocyanine Films

Abstract

Spectra of non-stationary light absorption ΔD induced by femtosecond laser pulses in lead phthalocyanine (PbPc) and chloro-aluminum-chloro-phthalocyanine (ClAlClPc) films have been studied. The 210-nm PbPc and 270-nm ClAlClPc films were thermally evaporated in a 6.5-mPa vacuum onto quartz substrates. "Hot" absorption bands induced by electron transitions from non-zero vibronic bands of state S1 into the zero vibronic band of state Sm were registered in the spectral interval of 2.04-2.37 eV. The dependences of the normalized kinetics ΔDn(t) were non-exponential for both films. The experimental curves ΔDn(t) for PbPc and ClAlClPc films are approximated by sums of two and three, respectively, exponents with different relaxation times. K e y w o r d s: Kohlrausch function (a "stretched" exponent), "pump-probe" technique, light absorption, PbPc and ClAlClPc films, femtosecond laser pulses, "hot" bands, temporal kinetics.