Regulating the femtosecond excited-state lifetime of a single molecule

The key to controlling reactions of molecules induced with the current of a scanning tunneling microscope (STM) tip is the ultrashort intermediate excited ionic state. The initial condition of the excited state is set by the energy and position of the injected current; thereafter, its dynamics determines the reaction outcome. We show that a STM can directly and controllably influence the excited-state dynamics. For the STM-induced desorption of toluene molecules from the Si(111)-7x7 surface, as the tip approaches the molecule, the probability of manipulation drops by two orders of magnitude. A two-channel quenching of the excited state is proposed, consisting of an invariant surface channel and a tip height–dependent channel. We conclude that picometer tip proximity regulates the lifetime of the excited state from 10 femtoseconds to less than 0.1 femtoseconds.

Source: ScienceNOW - September 6, 2018 Category: Science Authors: Rusimova, K. R., Purkiss, R. M., Howes, R., Lee, F., Crampin, S., Sloan, P. A. Tags: Chemistry, Physics reports Source Type: news