Andreas Strobel

High resolution photoelectron spectra of the NO dimer

High resolution zero kinetic energy (ZEKE) photoelectron spectra of the NO dimer are measured. They provide information about the ionization energy of the neutral, as well as about the binding energy, vibrations and structure of the ionized dimer indicating considerable structural reorganization of the dimer upon ionization.

The non-resonant two-photon zero kinetic energy photoelectron spectrum of CS2

Abstract The high-resolution zero kinetic energy photoelectron spectrum of CS 2 is presented. Accurate values for the ionization potential and the spin—orbit splitting of the X + 2 Π g are obtained. Observation of the symmetry-forbidden excitations of the v 2 bending vibration yields accurate frequencies for this normal mode. The Renner—Teller splitting for the Δ u 3 2 and the Σ − u components of v + 2 in the upper 2 Π g 1 2 spin—orbit component has been resolved for the first time. The photoionization efficiency spectra show a strong counter-correlation of the CS + 2 and S + fragments.

The nonresonant two‐photon zero kinetic energy photoelectron spectrum from the electronic ground state of H2S

The nonresonant two‐photon (1+1) ZEKE (zero kinetic energy) photoelectron spectrum from the X 1A1 electronic ground state of H2S is reported. Complete rotational resolution of the X 2B1 ground state of the ion was achieved for different temperatures in the jet. The ZEKE spectra show angular momentum transfer up to ΔN=2. The rotationalNKa+Kc++  ←  J″Ka″Kc″ branching ratios for the low‐lying rotational levels were determined. The strongest transitions are those with ΔKa=Ka+−Ka″=±1 and ΔKc=Kc+−Kc″=0 (type c transitions) but transitions with ΔKa=0  and  ΔKc=±1 (type a transitions) also show a surprisingly high intensity. Changes in Ka or Kc up to ±3 are observed. The two‐photon spectra are compared with those obtained via one‐photon VUV photoionization by other authors.

The nonresonant‐two‐photon zero kinetic energy photoelectron spectrum out of the 2Π1/2 electronic ground state of nitric oxide

The nonresonant‐two‐photon (1+1) zero kinetic energy (ZEKE) photoelectron spectrum out of the 2Π1/2 electronic ground state of nitric oxide is reported. The ZEKE spectra, obtained for different initial temperatures in the jet, show complete rotational resolution of the X 2Σ+ electronic ground state (v+=0) of the ion. Angular momentum transfers up to ΔJ=±7/2 are observed. The rotational J+←J‘ branching ratios determined for this ionization process from a valence state differ remarkably from those observed in two‐color resonant ZEKE spectra of electronically excited Rydberg states.

Resonance enhancement effects in coherent two‐photon ionization of CH3I

One‐color two‐photon zero kinetic energy (ZEKE)‐spectra of CH3I were obtained via an intermediate resonant state. In contrast to one‐photon spectra an intense progression in the totally symmetric C–I stretching mode ν3+ is observed. The observation can be explained by a resonant‐Raman like enhancement in the intermediate dissociative state.

The (NO)2 dimer and its ions: Is the solution near?

In this manuscript the available experimental and theoretical information on (NO)2 and its ions is summarized and reviewed, and high resolution two photon, one color photoelectron spectra of the dimer are presented. The new spectra yield a wealth of information about the dimer cation, including possibly all six of its vibrational frequencies as well as several anharmonic intermode constants. The most consistent interpretation of the contradictory data available in the literature and of the present results is to assign the gas phase photoelectron spectrum to cis–cis ionization, and the matrix spectra to the trans (NO)2+ ionic ground state. The similarity between the observed matrix frequencies with the gas phase values reflects the insensitivity of the NO stretching fundamentals of the dimer cation to conformation, a point of view supported by the results of theoretical calculations. Despite the problems of theory in computing properties of the (NO)2 species, the experimental structures and molecular const...

Two‐photon ionization and dissociation of ethyl iodide

Both spin–orbit states of C2H5I+, the X1 2E1/2 and the X2 2E1/2 electronic states, are studied by one‐color two‐photon ionization of ethyl iodide, utilizing the zero kinetic energy pulsed field ionization (ZEKE‐PFI) photoelectron technique. Compared with conventional photoelectron data the two‐photon spectra exhibit a more extensive vibrational structure mainly involving the C–I stretching and the C–C–I bending modes. This additional vibrational excitation in the two‐photon spectra is discussed in terms of mode selective resonance enhancement by the dissociative A‐state continuum. Accurate values for the vibrational frequencies and the ionization energies are obtained. The appearance of nontotally symmetric modes in the two‐color ZEKE spectra is reported.