Towards AttoChemistry: imaging orbitals on their natural timescale

Avner Fleischer, Physics and Optical Engineering, Ort Braude College, Karmiel, 21982, Israel

Electronic processes are at the heart of all phenomena in nature (except for nuclear processes). They are responsible for the emission of light, the photosynthesis of plants, and the transport of information in our nerves. In particular, the hoping of electrons between atoms, breaking existing chemical bonds and forming of new ones, is the driving force for all chemical reactions. The electronic density rearrangement that leads to the formation of a chemical bond is extremely fast, and occurs on a timescale of sub-femtoseconds (10-15 seconds) and possibly attoseconds (10-3 femtoseconds). The holy grail of attoChemistry, the field which studies the ultrafast electronic evolution of systems at the attosecond time scale, is to be able to construct an ultrafast "movie" of this electronic evolution.

In the talk I will describe how such a "movie" can be constructed, with the aid of one of the most fundamental quantum processes: tunnel ionization. Upon exposure to intense infrared laser fields, atoms and molecules ionize. Depending on the release time of the electron into the continuum, one of two scenarios might take place. In the first, the electron simply flies towards the detector. I will show that this electron carries significant fingerprints about the electronic orbital from which it was torn. By analyzing its properties (momentum, energy) in a COLTRIM (cold target recoil ion momentum) spectrometer, we essentially constructed a "laser-STM" – an analogue to the conventional STM - capable of studying electron dynamics with ultrafast temporal resolution. I will show how this machinery can be used to take femtosecond-resolution snapshots of an evolving electronic wavepacket density inside several atoms and molecules [1]. This work paves the way towards imaging of more complex electronic processes, such as charge transfer in molecules and semiconductor devices.

[1] A. Fleischer et al, "Probing Angular Correlations In Sequential Double Ionization", Phys. Rev. Lett. 107 113003 (2011).