52 research outputs found
High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis
We present a generic approach for treating the effect of nuclear motion in
the high-order harmonic generation from polyatomic molecules. Our procedure
relies on a separation of nuclear and electron dynamics where we account for
the electronic part using the Lewenstein model and nuclear motion enters as a
nuclear correlation function. We express the nuclear correlation function in
terms of Franck-Condon factors which allows us to decompose nuclear motion into
modes and identify the modes that are dominant in the high-order harmonic
generation process. We show results for the isotopes CH and CD and
thereby provide direct theoretical support for a recent experiment [Baker {\it
et al.}, Science {\bf 312}, 424 (2006)] that uses high-order harmonic
generation to probe the ultra-fast structural nuclear rearrangement of ionized
methane.Comment: 6 pages, 6 figure
Ionization of oriented targets by intense circularly polarized laser pulses: Imprints of orbital angular nodes in the 2D momentum distribution
We solve the three-dimensional time-dependent Schr\"{o}dinger equation for a
few-cycle circularly polarized femtosecond laser pulse interacting with an
oriented target exemplified by an Argon atom, initially in a or
state. The photoelectron momentum distributions show distinct
signatures of the orbital structure of the initial state as well as the
carrier-envelope phase of the applied pulse. Our \textit{ab initio} results are
compared with results obtained using the length-gauge strong-field
approximation, which allows for a clear interpretation of the results in terms
of classical physics. Furthermore, we show that ionization by a circularly
polarized pulse completely maps out the angular nodal structure of the initial
state, thus providing a potential tool for studying orbital symmetry in
individual systems or during chemical reactions
Ionization of 1D and 3D oriented asymmetric top molecules by intense circularly polarized femtosecond laser pulses
We present a combined experimental and theoretical study on strong-field
ionization of a three-dimensionally oriented asymmetric top molecule,
benzonitrile (CHN), by circularly polarized, nonresonant femtosecond
laser pulses. Prior to the interaction with the strong field, the molecules are
quantum-state selected using a deflector, and 3-dimensionally (3D) aligned and
oriented adiabatically using an elliptically polarized laser pulse in
combination with a static electric field. A characteristic splitting in the
molecular frame photoelectron momentum distribution reveals the position of the
nodal planes of the molecular orbitals from which ionization occurs. The
experimental results are supported by a theoretical tunneling model that
includes and quantifies the splitting in the momentum distribution. The focus
of the present article is to understand strong-field ionization from
3D-oriented asymmetric top molecules, in particular the suppression of electron
emission in nodal planes of molecular orbitals. In the preceding article
[Dimitrovski et al., Phys. Rev. A 83, 023405 (2011)] the focus is to understand
the strong-field ionization of one-dimensionally-oriented polar molecules, in
particular asymmetries in the emission direction of the photoelectrons.Comment: 12 pages, 9 figure
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