|
In the field of ultrafast spectroscopy different methods to calculate nonlinear spectra have been applied. Often perturbation theory in the electric field is used. This approach is compared with nonperturbative approaches where the signal field is constructed from the total field induced polarization of the system [1]. We show that for the pump-probe spectrum of a model system analogue results are achieved within the validity of the different approaches. Although the perturbation theory approach is faster for systems where the respective response function can be derived analytivcally, for real world systems and higher intensities nonperturbative approaches are the better choice [2,3]. This is demonstrated by the calculation of transient absorption spectra of Perylene and the comparison with recent experimental results. [1] B. Brüggemann, A. L. Dobryakov, N. P. Ernsting, and V. May: Calculating Femtosecond Transient Absorption Spectra: Non--Perturbative Methods Compared to the Third--Order Response Function Approach submitted. [2] B. Brüggemann, P. Kjellberg, and T. Pullerits: Nonperturbative calculation of 2D spectra in heterogeneous systems: Exciton relaxation in the FMO complex Chem. Phys. Lett. 444, 192 (2007). [3] B. Brüggemann, P. Persson, H.-D. Meyer, and V. May: Frequency dispersed transient absorption spectra of dissolved Perylene: A case study using the density matrix version of the MCTDH Method Chem. Phys. 347, 152 (2008). |
|