Vector-correlation in three particle continuum states
Final Report Abstract
In his doctoral thesis Fechner presents extensive experiments on the momentum correlation of three hydrogen atoms and shows that nodal lines in experimental MVC maps are in causal connection with nodal planes of the heavy-particle wavefunction describing the bound state of the molecule prior to dissociation. Since after dissociation fragment trajectories underly no internal or external forces, the momentum correlation observed at the macroscopic detector, which is meters away from the dissociation region, is also representative at shorter distance, - all the way to molecular distances at which the fragment energies ( typically 0.3 - 0.6 eV ) are large compared to the interaction energy between two hydrogen atoms (≈10 meV at 10 bohr). With Kemble’s concept of momentum measurement of a free quantum particle this permits to formulate a spatial many-body wavefunction at molecular distances (the edge of the reaction zone) purely from experimental data. In an optical analogue one may compare the macroscopic coincidence measurement with the observation of a Fraunhofer diffraction pattern. The latter is valid all the way down to the near field zone (Fresnel zone) at dimensions where the (deBroglie) wavelength is comparable to the size of the diffracting object (in our case the H3 molecule). Fechner formulates the spatial many-body wavefunctions at molecular distances in terms of the product of bound-state heavy-particle wave function in terms of a 3D harmonic oscillator and the bound-free coupling matrix element. The latter is so far available from theory only for vibronic dissociation. Once matrix elements are available for other non-adiabatic operators Fechner’s formalism will find application in comparison with electronic states other than s-Rydberg states of triatomic hydrogen. It is interesting to remark that since Fechners presentation quantum theory simulations have now progressed and Lehner and Jungen have in 2015 presented a three-dimensional wave packet method, based on Lanczos tridiagonalization of the Hamiltonian, which also includes the time dependent propagation on the ground state potential energy surfaces.
Publications
- Profound isotope effect in dissociation of triatomic hydrogen. J. Phys. Chem. A 117, 9794-9799 (2013)
P. C. Fechner, K. Mozer and H. Helm
(See online at https://doi.org/10.1021/jp312560t) - Imaging of spatial many-body wave functions via linear momentum measurements, Phys. Chem. Chem. Phys., 16 453-457 (2014)
P. C. Fechner and H. Helm
(See online at https://doi.org/10.1039/c3cp53300j)
