Ultrafast cascading theory of intersystem crossings in transition-metal complexes

Abstract

We investigate the cascade decay mechanism for ultrafast intersystem crossing mediated by the spin-orbit coupling in transition-metal complexes. A quantum-mechanical description of the cascading process that occurs after photoexcitation is presented. The conditions for ultrafast cascading are given, which relate the energy difference between the levels in the cascading process to the electron-phonon self energy. These limitations aid in the determination of the cascade path. For Fe 2+ spin-crossover complexes, this leads to the conclusion that the ultrafast decay primarily occurs in the manifold of antibonding metal-to-ligand charge-transfer states. We also give an interpretation for why some intermediate states are bypassed.

A Nonorthogonal State-Interaction Approach for Matrix Product State Wave Functions

“…Prime examples include the modeling of non-adiabatic dynamics processes 1,2 as well as light-induced excited spin-state trapping phenomena 3,4 . The theoretical description of these processes builds upon the calculation of intersystem crossing rates 5 which, besides electronic and vibronic coupling elements, requires the evaluation of spin-orbit (SO) coupling (SOC) matrix elements.…”

Computational approach to the study of thermal spin crossover phenomena

“…[4][5][6] This phenomenon, called Light-Induced Excited Spin State Trapping (LIESST), initially found in Fe(II) complexes [7][8][9][10][11] and later also observed in systems containing Fe(III), [12][13][14][15] and Ni(II) [16][17][18] has been intensively studied in the last years in order to unravel its mechanism both with experimental techniques 11,[19][20][21][22][23][24][25] and by means of theoretical calculations. [26][27][28][29][30][31][32][33] The most numerous and most studied family of SCO systems involves octahedral Fe(II) complexes in the solid state or in solution. The LS-HS transition in Fe(II) complexes is accompanied by an enlargement of the iron-ligand distances due to the occupation of antibonding e orbitals in the HS state.…”

Model of ultrafast demagnetization driven by spin-orbit coupling in a photoexcited antiferromagnetic insulator Cr2O3

“…24 The decay time of a photoexcited state strongly depends on the ratio of the energy gap to the electronphonon self-energy difference, which has been demonstrated in transition-metal complexes. 34 When the ratio ∆/ε ranges from 0.5 to 1.5, the fastest decay occurs. In engineering, the energy gap between the multiplets could be changed by distortion stress, strain or chemical substitution of ligands, which provides a feasible approach to adjust the demagnetization time.…”

“…We describe the time evolution of the local open quantum system with the dissipative Schrödinger equation 33,34 ih d|ψ(t) > dt…”

“…34,36 According to the Jablonski energy diagram, (2Γ) −1 ranges from 0.01 picosecond (ps) to 10 ps. In this paper, we set (2Γ) −1 = 0.1 ps.…”