Papers by Klaus Müller-dethlefs
SPringer series in optical sciences, 1987
Rotationally selective photoionization dynamics for the transition (NO+)X'Z+(v+ O, N+) (NO)A2Z+(v... more Rotationally selective photoionization dynamics for the transition (NO+)X'Z+(v+ O, N+) (NO)A2Z+(v =0,1V&,J& Nz+-, ') is studied by high-resolution zero-kinetic-energy photoelectron spectroscopy (ZEKE-PES). Two-photon, two-color photoionization via the NO A state in a skimmed supersonic jet is employed in the experiments. The observed angular momentum transfer ion molecule is found to depend strongly on the initial quantum number N&. The ioniza'tion potential is determined to be 74719.0 0.5 cm
Zeitschrift für Naturforschung, Nov 1, 1984
A novel method for the unambiguous direct determination of ionization potentials is presented. Th... more A novel method for the unambiguous direct determination of ionization potentials is presented. This is done by combining a pulsed field technique with a steradiancy analyser for the detection of threshold electrons. For now a resolution of better than 0.15 meV is demonstrated by resolving the first three rotational states of NO+.
Journal of Chemical Physics, Jun 1, 1993
Rotationally resolved zero kinetic energy-pulsed field ionization (ZEKE-PFI) photoelectron spectr... more Rotationally resolved zero kinetic energy-pulsed field ionization (ZEKE-PFI) photoelectron spectra of NH3 were obtained by nonresonant two-photon ionization from the X̃(1A1′) electronic ground state. The ZEKE spectra were recorded up to an internal ion energy of 9500 cm−1 by pulsed field ionization of long-lived Rydberg states of very high principal quantum numbers. Rovibronic bands of the NH3+ cation with v2+=1–9 (umbrella mode), v4+=1, and for the first time the mode ν1 in the combination band v+=1121 of the X̃+(2A2″) electronic ground state are observed in the ZEKE spectra. Rotational constants and band origins are determined in the analysis. The adiabatic ionization energy obtained by a recent ZEKE measurement is confirmed at 82 159±1 cm−1.
Physica Scripta, Jun 1, 1990
ABSTRACT
Chemical Physics Letters, Dec 1, 1984
... Two-colour photoionization resonance spectroscopy of NO: Complete separation of rotational le... more ... Two-colour photoionization resonance spectroscopy of NO: Complete separation of rotational levels of NO + at the ionization threshold. ... This was made possible by the application of a pulsed electric field discrimina tion teclmique in combination with a steradiancy ana lyser [8]. 2 ...
Springer eBooks, 1991
Bond-selective fragmentation of the molecules N-N-O, CF2=CH3andcF3-CH3is observed for site-specif... more Bond-selective fragmentation of the molecules N-N-O, CF2=CH3andcF3-CH3is observed for site-specific is excitation. Excitation at either the terminal or central N-atom in N2O, or at either the fluorinated or hydrogenated C-atom in CF2=CH2and CF3,-CH3shows that the molecule memorizes the initial site of energy deposition, hence a chemical “memory effect”.
Annual Review of Physical Chemistry, Oct 1, 1991
State selection in molecular systems has fascinated physisists and chemists since the advent of m... more State selection in molecular systems has fascinated physisists and chemists since the advent of molecular quantum mechanics. During the past two decades, the availability of high brightness excitation sources, like tunable narrow band lasers and monochromatized ...
Chemical Physics Letters, Aug 1, 1991
Abstract We report the first rotationally resolved angular distributions of near-zero kinetic ene... more Abstract We report the first rotationally resolved angular distributions of near-zero kinetic energy photoelectrons produced from ionization of the lowest rotational states ( N A =0, 1, 2 or 3) of the nitric oxide A 2 Σ + (ν A =0) state. The angular distributions, for the ion in the X + 1 Σ + (ν + =0, N + =0, 1, 2 or 3) state, agree well with a theoretical model proposed by McKoy and co-workers, with the exception of the ionizing N + = 0← N A =1 rotational transition. The latter transition exhibits an isotropic angular distribution, which seems to indicate some hitherto unobserved threshold dynamics.
Journal of Electron Spectroscopy and Related Phenomena, Dec 1, 1993
... We think that the applications of ZEKE thresh-148 EW Sc/tag ci aL/J. Electron Spectrosc. .Rel... more ... We think that the applications of ZEKE thresh-148 EW Sc/tag ci aL/J. Electron Spectrosc. .Relat. .Phenoin. ... (b) L. Zandee, RB Bernstein and DA Lichtin, J. Chem. Phys., 69 (1978) 3427. 25 (a) JT Meek, RK Jones and JP Reilly, J. Chem. Phys., 73 (1980) 3503. ...
The theoretical asperts of zero kinetic energy phtoelectron spectroscopy (PES) are outlined, and ... more The theoretical asperts of zero kinetic energy phtoelectron spectroscopy (PES) are outlined, and its advantages over conventional PES are summarised
In large molecules and molecular clusters, the rotational structure in ZEKE spectra is not always... more In large molecules and molecular clusters, the rotational structure in ZEKE spectra is not always fully resolved. However, the rotational structure, and hence rotational constants, can be obtained from deconvolution of the ZEKE band profile, provided the rotational states in the intermediate (neutral) state have been identified. In addition, we invoke a spectator model for the ZEKE transitions, which simplifies the selection rules toN -N-10-N + N-and K-K =-, where l () is the angular momentum (projection) quantum number of the spectator electron. We present first results of a fitting procedure for comparison with experimental ZEKE spectra of phenol complexes.
Angewandte Chemie, May 18, 1998
Diewesentlich bessere Auflosung der ZEKE-Spektroskopie ist einer ihrer Hauptvorteile gegenuber de... more Diewesentlich bessere Auflosung der ZEKE-Spektroskopie ist einer ihrer Hauptvorteile gegenuber der herkommlichen Photoelektronen(PE)-Spektroskopie. Ein Vergleich eines PE-Spektrums von NO mit dem entsprechenden ZEKE-Spektrum verdeutlicht dies (siehe rechts). Die ZEKE-Spektroskopie last sich unter anderem anwenden bei der Charakterisierung von Molekulen, H-Brucken-gebundenen Clustern wie Phenol-Wasser, Ubergangsmetall-Clustern, van-der-Waals-Komplexen wie Benzol-Argon und sogar reaktiven Intermediaten.
Journal of Electron Spectroscopy and Related Phenomena, Jul 1, 2000
The study of molecular complexes in their cationic states has been considerably advanced by the d... more The study of molecular complexes in their cationic states has been considerably advanced by the development of zero electron kinetic energy (ZEKE) photoelectron spectroscopy due to its high resolution and state selectivity. In this report, we apply ZEKE spectroscopy to the phenol?Ar complex to investigate whether the system exists in multiple isomeric forms under supersonic jet conditions. ZEKE spectra are recorded via four intermediate levels of the S excited state of the neutral. 1 All four ZEKE spectra display vibrational progressions in the same three intermolecular modes, namely the b bend (15 x 21 21 21 cm), the b bend (25 cm) and the s stretch (66 cm) which are consistent with a 'van der Waals' structure where the y z Ar atom binds above the aromatic ring. We discuss the absence of the hydrogen-bonding phenol?Ar structure, and suggest experimental routes that could be employed to observe this isomer.
Chemical Physics Letters, Oct 1, 1994
Abstract Basic principles of the ZEKE (zero kinetic energy photoelectron) spectroscopic method ar... more Abstract Basic principles of the ZEKE (zero kinetic energy photoelectron) spectroscopic method are outlined. The experimental procedure takes advantage of specially tailored electric field ionization pulses. Two types of extraction pulses are considered: (i) linearly rising pulses (‘linear slope’) and (ii) pulses with a multi-step ‘staircase slope’. First, the dependence of the spectral ZEKE resolution on both linear slope pulses with different rise times and staircase slope pulses with varying step height is described. Secondly, the staircase slope pulse is used for an accurate determination of the ionization energy by measuring the ZEKE signals correlated to different field strengths simultaneously in one single scan. For the benzene molecule a predominantly diabatic ionization process (field shift equation: ΔE/cm−1 = (3.89±0.05) (F/V cm−1) 1 2 ) is observed.
Journal of Chemical Physics, May 1, 1987
Rotationally selective photoionization dynamics for the transition (NO+)X'Z+(v+ O, N+) (NO)A2Z+(v... more Rotationally selective photoionization dynamics for the transition (NO+)X'Z+(v+ O, N+) (NO)A2Z+(v =0,1V&,J& Nz+-, ') is studied by high-resolution zero-kinetic-energy photoelectron spectroscopy (ZEKE-PES). Two-photon, two-color photoionization via the NO A state in a skimmed supersonic jet is employed in the experiments. The observed angular momentum transfer ion molecule is found to depend strongly on the initial quantum number N&. The ioniza'tion potential is determined to be 74719.0 0.5 cm
Berichte der Bunsengesellschaft für physikalische Chemie, Aug 1, 1981
Local temperatures and hydrogen concentrations in an ethylene‐air Bunsen flame have been determin... more Local temperatures and hydrogen concentrations in an ethylene‐air Bunsen flame have been determined from CARS measurements of the Q(0) to Q(4) [υ = 1 ← υ = 0] Raman transitions in hydrogen. A crossed beam, BOXCARS, technique of high spatial resolution including non‐resonant background cancellation is employed. The linewidth correction is taken into account for the limit of Doppler broadening. The results agree well with thermodynamic equilibrium calculations.
European Conference on Atomic Physics, 1981
Berichte der Bunsengesellschaft für physikalische Chemie, Mar 1, 1985
We evaluate the CARS rotational line‐strength for a CARS triple resonance with arbitrary laser po... more We evaluate the CARS rotational line‐strength for a CARS triple resonance with arbitrary laser polarizations and for Hund's coupling cases (a) or (b). The intermediate case (a)—(b) coupling result is given for a 2Σ+← 2Π transition corresponding to OH or NO.
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Papers by Klaus Müller-dethlefs