Femtosecond spectroscopy of vanadyl phthalocyanines in various molecular arrangements

Ultrafast excitation relaxation in titanylphthalocyanine thin film

“…The relaxation mechanism of the light-induced excitations is one of the most important factors determining the optical properties and potential applications of such materials. Several studies in femtosecond domain have been reported on the ultrafast excited-state dynamics of phthalocyanine film [4][5][6][7][8][9]. Ho and Peyghambarian [4] found that the polycrystalline AlClPc film possesses two extremely fast routes of ground state recovery, i.e., a fast exciton-exciton annihilation which determines the subpicosecond kinetics at high excitation intensities and the linear relaxation on the picosecond time scale due to exciton-phonon coupling.…”

Effect of axial substitution on the ultrafast dynamics and third-order optical nonlinearity of metallophthalocyanines films

“…The excitons in the Q-band were then thought to relax back to the ground state via excitonexciton annihilation (E-EA), internal conversion and inter-system crossing (ISC). The E-EA rate GðtÞ is a time-dependent rate, ft À0.5 , where the annihilation is via the long-range dipole-dipole interaction between excitons or motion-limited diffuse [5,6]. By fitting the data with numerical solution for the dynamic equations of the model, the E-EA and the ISC rate can be found and are listed in Table 1.…”

“…Till now, a lot of research works on the ultrafast dynamics of phthalocyanines have been successfully carried out and many mechanisms have been proposed to elucidate the decay processes of the excited state [1][2][3][4][5][6]. Apparently, the modification and substitution of MPcs can affect these processes and thus become an attractive topic when the applications, such as optical communications, are concerned.…”

Parametric interactions and nonlinear Raman processes of vibronic excitons in polydiacetylene studied with a two‐optical‐cycle laser

“…1 Introduction It has been well known that the lifetimes of molecular excited states and Frenkel excitons are reduced under high-density excitation in aromatic molecular crystals such as anthracene [1,2], pyrene [3], fluoranthene [4], a charge-transfer complex [5], J aggregates [6], and polymers [7][8][9][10][11]. The mechanism of the lifetime shortening is well established to be the Auger process, in which one of two neighboring excitations (excited molecules or Frenkel excitons) are excited to a higher excitation (higher electronic excited state in a molecule or an excited exciton state) and the other to the ground state by the transition dipole-transition dipole interaction [1][2][3][4].…”

“…The mechanism of the lifetime shortening is well established to be the Auger process, in which one of two neighboring excitations (excited molecules or Frenkel excitons) are excited to a higher excitation (higher electronic excited state in a molecule or an excited exciton state) and the other to the ground state by the transition dipole-transition dipole interaction [1][2][3][4]. The higher excitations are expected to relax very rapidly to the lowest excited state or the lowest exciton state, resulting in the shortening of the lifetime of the excitations [4,5,8,9].…”