Photoionization Of Xenon Research Articles

An integrated ion trap for the photon-ion spectrometer at PETRA III.

We have added a multipole ion trap to the existing photon-ion spectrometer at PETRA III (PIPE). Its hybrid structure combines a ring-electrode trap with a segmented 16-pole trap. The interaction of gases and ions with extreme ultraviolet radiation from the beamline P04 is planned to be investigated with the newly installed multipole trap. The research focus lies on radiation-induced chemical reactions that take place in the interstellar medium or in the atmospheres of planets, including natural as well as man-made processes that are important in the Earth's atmosphere. In order to determine the mass-to-charge ratio of the stored ions as efficiently as possible, we are using an ion time-of-flight spectrometer. With this technique, all stored ions can be detected simultaneously. To demonstrate the possibilities of the trap setup, two experiments have been carried out: The photoionization of xenon and the ion-impact ionization of norbornadiene. This type of ion-impact ionization can, in principle, also take place in planetary atmospheres. In addition to ionization by photon or ion impact, chemical reactions of the trapped ions with neutral atoms or molecules in the gas phase have been observed. The operation of the trap enables us to simulate conditions similar to those in the ionosphere.

Effect of SOIAIC on photoionization time delay of the Xe 3d subshell

SynopsisThe effect of spin-orbit activated interchannel coupling (SOIAIC) has been studied on the time delay spectrum of 3d photoionization in xenon. The relativistic-random-phase-approximation with relaxation (RRPA-R) has been used to calculate the Wigner-Eisenbud-Smith (WES) time delay in photoionization. SOIAIC has a strong influence on the WES time delay for all ejection angles of the photoelectrons with respect to the incident direction and the polarization vector of the photon absorbed.

Sub-cycle electron control in the photoionization of xenon using a few-cycle laser pulse in the mid-infrared

Using few-cycle laser pulses generated by optical parametric chirped pulse amplification, sub-cycle light-wave control of electrons was achieved at a carrier wavelength of 2.1 μm. We demonstrate the sub-cycle light-wave control in the case of strong field ionization of xenon atoms. Angle-resolved spectra of electrons emitted in the photoionization process were recorded as a function of the carrier-envelope phase (CEP) using an electron imaging technique. We observed a clear CEP-dependent asymmetry in the electron momentum distribution.

Coincident energy and angular distributions in xenon 4d5/2 inner-shell double photoionization

We report on measurements of the triply differential cross section for the 4d5/2 inner-shell photoionization in xenon followed by N5O2,3O2,3 Auger decay using electron–electron coincidence spectroscopy. The experimental setup made it possible to obtain the first coincident angular distributions for the (1D2) and (3P2) final states at a photon energy of 97.45 eV. Relative amplitudes and phases describing the photoionization were estimated from these angular distributions.

Semiclassical description of photoionization microscopy

Recently, experiments have been reported where a geometrical interference pattern was observed when photoelectrons ejected in the threshold photoionization of xenon were detected in a velocity-map imaging apparatus [C. Nicole et al., Phys. Rev. Lett. 88, 133001 (2002)]. This technique, called photoionization microscopy, relies on the existence of interferences between various trajectories by which the electron moves from the atom to the plane of observation. Unlike previous predictions relevant to the hydrogenic case, the structure of the interference pattern evolves smoothly with the excess energy above the saddle point and is only weakly affected by the presence of continuum Stark resonances. In this paper, we describe a semiclassical analysis of this process and present numerical simulations in excellent agreement with the experimental results. It is shown that the background contribution dominates in the observations, as opposed to the behavior expected for hydrogenic systems where the interference pattern is qualitatively different on quasidiscrete Stark resonances.

The power and beauty of (γ, 2e) experiments

The power and beauty of energy- and angle-resolved two-electron emission in the double photoionization of atoms is demonstrated, concentrating on the particular shapes of the angular correlation patterns of the triple differential cross section. The cases selected are direct double photoionization in helium and neon as well as sequential double photoionization in xenon, both for equal and unequal energies of the emitted electrons.

Manifestation of Strongly Delocalized Atomic States in the5sPhotoionization of Xenon

The photoionization (PI) of the Xe atom was investigated in the vicinity of the $5s$-shell threshold by photon-induced fluorescence spectroscopy. The highest resolution so far attained of 2 meV enabled us to observe a new series of resonance structures in the $5s$-PI cross section closely above threshold. Calculations of the partial $5s$- and $5p$-PI cross sections were performed taking into account many-electron correlations. These structures were related with strongly delocalized $f$-resonances which affect the $5s$-PI cross section due to their mixing with $p$-resonances.

Matrix elements for photoionization in xenon derived from coincidence electron spectrometry

The magnitudes and relative phases of the matrix elements pertaining to photoionization in xenon at 132.2 eV photon energy have been derived from observables in an angle-resolved electron spectrometry experiment. The observables in question are the partial cross section, the angular distribution parameter of the photoelectron, the alignment parameter of the photoion, and the angular correlation between the photoelectron and the coincident Auger electron. Difficulties in extracting the desired matrix elements from these observables are discussed. Despite these difficulties, a set of matrix elements and relative phases could be extracted which is in good agreement with all experimental observables and also fulfils the constraint that spin - orbit effects in the photoelectron's partial waves be negligible. This data set differs significantly from theoretical predictions from relativistic random-phase calculations.

Stochastic field effects and transform-limited laser pulses

In many ultrashort-laser-pulse experiments the field is transform limited, and under these conditions it is usually assumed that the stochastic nature of the field can be ignored in the interpretation of experimental data. We theoretically consider the 3 + 2 photoionization of xenon, using a pulsed stochastic field. Our results show that the field's stochastic nature always has an effect on the ac Stark shift modification factor Re(M), no matter what the pulse width, and that a short-pulse approximation to Re(M) can require a Fourier-transform bandwidth 1000 times larger than the laser's intrinsic (cw) spectral width.

Comment on ‘‘Complete fragmentation pattern for two-step double photoionization in Xenon’’

Comment on ‘‘Complete fragmentation pattern for two-step double photoionization in Xenon’’

Complete fragmentation pattern for two-step double photoionization in xenon.

An extensive study of the 4${\mathit{f}}_{5/2}$ photoionization in xenon is presented which allows, through the observation of the coincident ${\mathit{N}}_{5\mathrm{\ensuremath{-}}}$${\mathrm{O}}_{23}$${\mathrm{O}}_{23}$ $^{1}$${\mathit{S}}_{0}$ Auger electron, the establishment of the first complete fragmentation pattern for two-electron emission with information on the momenta and the spin projections of both electrons.