title: Electric field allowed molecular transitions for one and two photon excitation microscopy.
abstract: We propose an excitation technique for observing single and two photon excitation in those molecules for which such transitions are forbidden by the selection rules. This is possible by the application of an external electric field that perturbs the molecular orbitals, thereby resulting in a significant shift of energy levels. Such a shift of energy levels may bring those levels in resonance with the radiation field which is normally forbidden by selection rules. Further, parity of the these states may significantly improve the emission process. The external electric field results in the mixing of excited (short lifetime) and metastable states (long lifetime), thus reducing the lifetime of metastable (or near metastable) states. This may provide an effective channel for allowing transition from the metastable states. An application of electric field may result in the excitation of poorly excitable biomolecules. This excitation technique may find applications in single- and multi-photon fluorescence microscopy, bioimaging and optical devices.
authors: International Center for Theoretical Physics, Trieste, Italy. partha@fisica.unige.it
authors: Partha Pratim
authors: PP
authors: Mondal
authors: Alberto
authors: A
authors: Diaspro
mesh_terms: D003198:Computer Simulation; D004563:Electrochemistry / Q000379:methods*; D004574:Electromagnetic Fields; D005456:Fluorescent Dyes / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D008956:Models, Chemical
chemical_list: D005456:Fluorescent Dyes