Direct Probe of the Shape Resonance Mechanism in2σg-Shell Photoionization of theN2Molecu

Abstract

Angular distributions of photoelectrons from a 2sigma(g) shell of fixed-in-space N2 molecules have been measured for left- and right-elliptically polarized and for linearly polarized light at several photon energies in the region of sigma(*) shape resonance. That allowed the determination of a set of dipole matrix elements and phase shift differences characterizing the process. These data clearly show the enhancement of the fsigma(u) partial cross section in the resonance simultaneously with an abrupt increase of the corresponding phase shift by pi, which is the first experimental demonstration of the nature of the sigma(*) shape resonance in homonuclear diatomic molecules.

Recoil-ion and electron momentum spectroscopy: reaction-microscopes

“…By combining linearly and circularly polarized light, the amplitudes and phases of the different angular momentum partial waves can be measured (Gessner et al 2002;Jahnke et al 2002;Motoki et al 2002). In addition, the electron wavelength can be scanned by scanning the photon energy.…”

“…Electron angular distributions for molecules fixed in space by detection of the molecular fragments have been first performed by Shigemasa and coworkers with traditional analyzers for electrons and ions (Shigemasa et al 1995) (see also Shigemasa et al (1998); Watanabe et al (1997); Cherepkov et al (2000); Cherepkov et al (2000a); Ito et al (2000); Ito et al (2000a); Motoki et al (2002) for later experiments by this group). One other group has combined timeof-flight electron spectrometers (Golovin et al 1997;Heiser et al 1997;Gessner et al 2002) with imaging of the molecular fragments.…”

Electron angular distribution in dissociative photoionization of fixed in space D2molecules induced by circularly polarized light

“…Briefly, the final state comes from a close-coupling calculation incorporating contributions from the two lowest ionization thresholds of H 2 the molecule dissociates as well as interferences among the various electronic and nuclear channels. B-spline functions were used to obtain the electronic and vibrational wave functions.…”

“…Its occurrence in PI of oriented achiral molecules is a consequence of the spatial non-coplanarity of three vectors: the light propagation vector of elliptically polarized light k, the photoelectron momentum k e , and the molecular axis n, which creates a handedness for the system [1]. The CDAD observation for randomly oriented achiral molecules has been studied by recording MF photoelectron angular distributions (MFPADs), taking advantage of dissociative photoionization (DPI) induced by absorption of X/VUV circularly polarized synchrotron radiation for inner shell [2][3][4] and outer shell [5][6][7] PI. The triplet (k e , n, k) is identified by measuring in coincidence the initial velocity vectors of the photoion and photoelectron for each DPI event.…”

“…The triplet (k e , n, k) is identified by measuring in coincidence the initial velocity vectors of the photoion and photoelectron for each DPI event. These studies focused on the dynamics of the PI reaction, along the shape resonance region associated with the ionized orbitals [2,3,5], in the region above the respective ionisation thresholds [4,6], or at resonance with discrete autoionizing states where interferences between resonant and non resonant ionisation occur [7]. They were motivated by the fact that the MFPADs obtained for PI induced by circularly polarized light give the most complete access to the dipole matrix elements of the transition, their magnitudes and phase shifts [2][3][4][5][6][7].…”