Stuttgart 2012 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Poster 1: Cold Molecules, Femtosecond Spectroscopy, Molecular Dynamics

MO 13.25: Poster

Tuesday, March 13, 2012, 16:30–19:00, Poster.IV

High Harmonic Spectroscopy of NO₂: Electronic Dynamics and Molecular Dissociation — •Chung-Hsin Yang¹, Christian Neidel¹, Jesse Klei¹, Arjan Gijsbertsen³, Marc Vrakking¹, and Hans Jakob Wörner² — ¹Max-Born-Institut, Berlin — ²ETH, Zürich — ³AMOLF, Amsterdam

Time-resolved photoelectron and photoion velocity map imaging (VMI) experiments have been used to study NO₂ excited close to its first dissociation limit, leading to NO (XΠ) and O (3P) fragments. The NO₂ molecule was excited to its A ²B₂ excited electronic state by one pump photon at a center wavelength of 395 nm, followed by a probe laser pulse in the XUV wavelength region from a high-harmonics source. The first excited electronic state of NO₂, A ²B₂, is embedded within the X ²A₁ electronic ground state and is strongly coupled to the X ²A₁ state via a conical intersection between the two potential energy surfaces. By varying the time delay between the pump and probe lasers, we probe the photodynamics of NO₂ by measuring photoion and photoelectron momentum distributions. In our measurements, both NO⁺ and O⁺ yields show exponential growth ( 1-1.5ps rise time) corresponding to the dissociation time scale observed from previous energy dependence studies. For the photoelectron results, some channels with hundred femtoseconds or picoseconds dynamics have been ascribed to the ionization of NO₂ molecule in X ²A₁ or A ²B₂ state, or fragments. However, contributions from electrons correlating with different ions and produced by different high harmonics result in a large complexity of photoelectron images.