Multiphoton ionization of unsaturated hydrocarbons

Abstract

A formalism for predicting the rate of multiphoton ionization of unsaturated hydrocarbons was developed. The model was tested on benzene and pyridine for example. The theoretically calculated ion yield versus intensity curves show excellent agreement with the experimentally obtained curves using 200 fs Ti:sapphire laser pulses.

Nonlinear Ionization of Organic Molecules in High Intensity Laser Fields

“…For all of the organic molecules studied, we find that I sat is greater than that predicted by ADK theory by as much as 5 times. Although it is harder to define a saturation intensity with their focused beam geometry, results similar to ours on much smaller sets of molecules are implicit in the data and the analysis of Chin and co-workers [13,18,19] and Ledingham and co-workers [20]. O 2 and to some extent HCl are the only molecules where suppressed ionization has been remarked on directly [18,21].…”

“…The diatomics O 2 and HCl were found to ionize at higher intensity than would be implied by ADK tunneling calculations [18,21]. Although there are many models for tunnel ionization of neutral molecules [10,13], to our knowledge, this apparently general phenomenon has never been predicted.…”

“…There has been a great deal of discussion on the alignment sensitivity to strong field femtosecond laser ionization [10,[12][13][14] based on model calculations. Furthermore, it is well known that ionization of dissociating molecular ions is very sensitive to alignment [15].…”

Nonadiabatic Multielectron Dynamics in Strong Field Molecular Ionization

“…Here v L is the laser frequency and t t is the atomic tunneling time: t t p 2I p ͞E where I p is the ionization potential and E is the laser field strength (atomic units). The strong field ionization of molecules has also largely been modeled within this quasistatic picture, with corrections [8,9] to account for the extended molecular geometry and polarizability, including modification of the Keldysh parameter [8]. However, in polyatomic molecules with many delocalized electrons neither the single active electron nor quasistatic perspectives may remain reliable, even in low-frequency fields.…”

Application of Short Laser Pulses

“…3. Talebpour et al (1998b) have argued that the ionization amplitude can be thought as being a linear superposition of the ionization amplitudes of individual stared atoms. The MPI process in an unsaturated hydrocarbon might be considered as the emission of electron waves from multiple centers.…”