Molecular Physics Seminar

Title: Imaging the Three-Body Wavefunction of Fragmenting Triatomic Hydrogen

Speaker: Steffen Meyer, Albert-Ludwigs-Universität Freiburg, Germany

Abstract:

Neutral triatomic hydrogen is the most simple polyatomic molecule, and a prototype of molecular degrees of freedom, of molecular interaction and of nonadiabatic couplings in particular. I will begin my presentation by outlining fundamental properties of this molecule and then concentrate on my current research theme and experiment in Freiburg where I study three-body fragmentation of electronically excited states of H₃. My specific interest is in states with principal quantum number n = 4 which I excite using a narrowband tunable diode laser in a keV neutral beam. The excited states decay primarily by predissociation into the continuum of three neutral H atoms. Time- and position-sensitive detectors allow to record in coincidence the three slow (? 1 eV) neutral ground state hydrogen atoms which emerge in predissociation. Coincident detection of the three correlated atoms from a single molecule permits to reconstruct the centre-of-mass momentum vectors of the three hydrogen atoms. This experiment, when repeated for many molecules (typically 10⁴) delivers a map of momentum correlation of the three H atoms. This momentum correlation map may be regarded as an image of the modulus squared of the three-body wavefunction, at the time when the system emerges from molecular distances. As the bound state heavy-particle wavefunction is known, the observed distribution is a measure of the phase-space dependent action of nonadiabatic coupling which allows the bound state to exit into the continuum.

Coffee/tea will be served at 13:05