Definition of the molecular frame, , (a) for a molecule in the or the symmetry group and (b) for symmetry. is the angle between the symmetry axis and the bond, and is half of the bond angle. and (Ref. 33 ) in the ground state of ammonia.
Analytical profiles for linear molecules for (a) and (b) transitions for the vector parallel to the spectrometer axis.
Total ion-yield spectrum of ammonia at the N ionization edge, measured with the spectrometer mounted with the axis parallel to the polarization direction and perpendicular to the propagation direction of the synchrotron light. The intensities are corrected for the photon flux but not for the variation in gas pressure. The peaks are identified in Table I .
The PEPICO spectra measured in the plane of polarization after core excitation to the (a) and (b) orbitals. The “time” axis is rescaled to show the mass of the fragments.
Electron-ion-ion coincidence maps measured after decay of excited states of the ammonia molecule. The number of , events are plotted in the contour diagrams. In panel (a) the pair from the decay of the state is displayed, and in (b) the reaction from the same state is shown while in (c) the pair is presented. In panels (d)–(f) the same channels measured after excitation to the N state are shown. In the inset the and projections are shown. Each of these coincidence channels involves detection of an fragment thus the abscissa is the same for each plot. The ordinate axes are scaled in the same way for each fragment. The flight times are not absolute due to a zero offset.
PEPIPICO measurements at energies within the and peaks in Fig. 3 . The plot shows the projection of the three dimensional event map to two dimensions. Both of the states are studied using three different photon energies: at the resonance maximum, detuned below the maximum and above. The experimental data are shown with circles and the simulation is the dashed line. A compilation of the parameters used to perform the simulations is given in Table IV .
PEPIPICO measurements of the fragments at the (a) N peak at , (b) N , at , and (c) N at resonances and (d) at . The circles represent the projected experimental data and the simulation is shown using a dashed line. A compilation of the parameters used to perform the simulations can be found in Table V .
Assignments of the features in the absorption spectrum. The notation reflects the electronic state (peaks 1 and 2, Ref. 20 ) or the transition from the level. The most recent work appears to the left.
The peak widths for the ion-electron coincidence peaks in Fig. 4 .
The parameters used for the simulations of the projected ion-ion coincidence spectra shown in Fig. 6 . In the ground state is 68°. The error in the angle is , and in the energy released the error is .
The parameters used in the simulations of the projected ion-ion coincidence spectra shown in Fig. 7 .
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