Multiple ionization and fragmentation dynamics of molecular iodine studied in IR-XUV pump-probe experiments.

The ionization and fragmentation dynamics of iodine molecules (I(2)) are traced using very intense (∼10(14) W cm(-2)) ultra-short (∼60 fs) light pulses with 87 eV photons of the Free-electron LASer at Hamburg (FLASH) in combination with a synchronized femtosecond optical laser. Within a pump-probe scheme the IR pulse initiates a molecular fragmentation and then, after an adjustable time delay, the system is exposed to an intense FEL pulse. This way we follow the creation of highly-charged molecular fragments as a function of time, and probe the dynamics of multi-photon absorption during the transition from a molecule to individual atoms.

Electron rearrangement dynamics in dissociating I(2)

The charge rearrangement in dissociating I_{2}^{n+} molecules is measured as a function of the internuclear distance R using extreme ultraviolet pulses delivered by the free-electron laser in Hamburg. Within an extreme ultraviolet pump-probe scheme, the first pulse initiates dissociation by multiply ionizing I_{2}, and the delayed probe pulse further ionizes one of the two fragments at a given time, thus triggering charge rearrangement at a well-defined R. The electron transfer between the fragments is monitored by analyzing the delay-dependent ion kinetic energies and charge states. The experimental results are in very good agreement with predictions of the classical over-the-barrier model demonstrating its validity in a thus far unexplored quasimolecular regime relevant for free-electron laser, plasma, and chemistry applications.

Time-resolved measurement of interatomic coulombic decay in Ne2.

The lifetime of interatomic Coulombic decay (ICD) [L. S. Cederbaum et al., Phys. Rev. Lett. 79, 4778 (1997)] in Ne2 is determined via an extreme ultraviolet pump-probe experiment at the Free-Electron Laser in Hamburg. The pump pulse creates a 2s inner-shell vacancy in one of the two Ne atoms, whereupon the ionized dimer undergoes ICD resulting in a repulsive Ne+(2p(-1))-Ne+(2p(-1)) state, which is probed with a second pulse, removing a further electron. The yield of coincident Ne+-Ne2+ pairs is recorded as a function of the pump-probe delay, allowing us to deduce the ICD lifetime of the Ne2(+)(2s(-1)) state to be (150±50) fs, in agreement with quantum calculations.

Second-order autocorrelation of XUV FEL pulses via time resolved two-photon single ionization of He.

Second-order autocorrelation spectra of XUV free-electron laser pulses from the Spring-8 Compact SASE Source (SCSS) have been recorded by time and momentum resolved detection of two-photon single ionization of He at 20.45 eV using a split-mirror delay-stage in combination with high-resolution recoil-ion momentum spectroscopy (COLTRIMS). From the autocorrelation trace we extract a coherence time of 8 ± 2 fs and a mean pulse duration of 28 ± 5 fs, much shorter than estimations based on electron bunch-length measurements. Simulations within the partial coherence model [Opt. Lett. 35, 3441 (2010)] are in agreement with experiment if a pulse-front tilt across the FEL beam diameter is taken into account that leads to a temporal shift of about 6 fs between both pulse replicas.

Ion-ion coincidence studies on multiple ionizations of N(2) and O(2) molecules irradiated by extreme ultraviolet free-electron laser pulses.

We have investigated multiple ionization of N(2) and O(2) molecules by 52 nm extreme-ultraviolet light pulses at the free-electron laser facility SCSS in Japan. Coulomb break-up of parent ions with charge states up to 5+ is found by the ion-ion coincidence technique. The charge-state dependence of kinetic energy release distributions suggests that the electrons are emitted sequentially in competition with the elongation of the bond length.

Ultrafast extreme ultraviolet induced isomerization of acetylene cations.

Ultrafast isomerization of acetylene cations ([HC=CH](+)) in the low-lying excited A(2)Σ(g)(+) state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C(+) + CH2(+) as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15 fs in a kinetic energy release (KER) window of 5.8

Three-dimensional momentum imaging of electron wave packet interference in few-cycle laser pulses.

Using a reaction microscope, three-dimensional (3D) electron (and ion) momentum (P) spectra have been recorded for carrier-envelope-phase (CEP) stabilized few-cycle ( approximately 5 fs), intense ( approximately 4 x 10(14) W/cm2) laser pulses (740 nm) impinging on He. Preferential emission of low-energy electrons (E(e)<15 eV) to either hemisphere is observed as a function of the CEP. Clear interference patterns emerge in P space at CEPs with maximum asymmetry, interpreted as attosecond interferences of rescattered and directly emitted electron wave packets by means of a simple model.

Few-photon multiple ionization of N2 by extreme ultraviolet free-electron laser radiation.

Few-photon multiple ionization of N2 was studied differentially in a reaction microscope using 44 eV, approximately 25 fs, intense ( approximately 10(13) W/cm(2)) photon pulses from FLASH. Sequential ionization is observed to dominate. For various intermediate charge states N(2)(n+0 we find a considerable excess of photons absorbed compared to the minimum number that would energetically be required. Photoionization of aligned N(2)(n+) ions, produced by photon absorption in sequential steps, is explored and few-photon absorption pathways are traced by inspecting kinetic energy releases and fragment-ion angular distributions.

Recoil-ion momentum distributions for two-photon double ionization of He and Ne by 44 eV free-electron laser radiation.

Recoil-ion momentum distributions for two-photon double ionization of He and Ne (variant Planck's over omega=44 eV) have been recorded with a reaction microscope at FLASH (the free-electron laser at Hamburg) at an intensity of approximately 1 x 10(14) W/cm2 exploring the dynamics of the two fundamental two-photon-two-electron reaction pathways, namely, sequential and direct (or nonsequential) absorption of the photons. We find strong differences in the recoil-ion momentum patterns for the two mechanisms pointing to the significantly different two-electron emission dynamics and thus provide serious constraints for theoretical models.

Cimetidine and chlorpheniramine in the treatment of psoriasis.

We examined the efficacy of cimetidine and chlorpheniramine alone and in combination in the treatment of psoriasis under the conditions of a randomised controlled double-blind study. Analysis of data from 52 patients revealed that none of the treatment regimes showed a demonstrable beneficial effect on the course of the psoriasis.

[Cystic acne and clinocomptodactyly in Klinefelter's syndrome (46XY/47 XXY mosaic)]. / Zystische Akne und Klinokamptodaktylie bei Klinefelter-Syndrom (46 XX/47 XXY Mosaik).

Klinefelter's syndrome was found in a 18 year old patient, suffering for four years from nodulocystic acne. Serum gonadotropins were within normal range, while histology of the testes revealed beginning tubular hyalinization. The case report shows that young patients with Klinefelter's syndrome may present symptoms that seem to exclude this syndrome. Furthermore, our patient exhibited klinokamptodaktylia of hands and feet, a congenital anomaly occurring very rarely in Klinefelter's syndrome.

[Treatment of psoriasis using vitamin A, vitamin A acid and oral retinoids]. / Behandlung der Psoriasis mit Vitamin A, Vitamin-A-Säure und oralen Retinoiden.

Vitamin A, Vitamin A acid (retinoic acid) and their synthetic derivatives were variously applied in the management of psoriasis with different therapeutic results. Obviously, they influence the proliferation rate and the differentiation of human keratinizing epithelia and have beneficial effects on skin diseases with disturbances of keratinization, including psoriasis. Systemic application of Vitamin A has been yet largely abandonned since high dosages leading to clearing develop evident systemic toxicity. The anti-psoriatic effect of Vitamin A acid is either moderate or restricted, because of side effects. Only its combined local application with topical corticosteroids may be considered. Oral application of newly synthesized retinoids, however, was beneficial in psoriasis, particularly in erythrodermic or pustular types. With this group of retinoids new pathways were opened in dermatotherapy which may help to replace cytostatic drugs in these cases. Additionally, oral retinoid treatment may be introduced as an adjuvans in the management of widespread psoriasis, in order to enhance the effect of anthralin, PUVA or UVB treatments.

Oral treatment of keratosis follicularis with a new aromatic retinoid.

Four patients with extensive keratosis follicularis (Darler's disease) showed excellent clinical response to the oral administration of a new aromatic derivative of retinoic acid (RO 10-9359). Initial oral treatment with 50 to 75 mg of the drug was followed by substantial improvement in four to seven days and the lesions cleared completely after three to four weeks. Long-term treatment with 25 to 30 mg/day was sufficient to prevent recurrence. No serious side effects were seen with this dosage after several months. Some dryness of the lips and the nasal mucosa occurred and one patient experienced slight nausea. Histological investigations showed the gradual disappearance of acantholysis, dyskeratosis, and hyperkeratosis, in this order. The given therapeutic schedule is a reliable routine management for keratosis follicularis in adults.

[Vitamin A acid for the topical management of epithelial neoplasms. Combination with 5-fluorouracil]. / Vitamin-A-Säure zur Lokalbehandlung epithelialer Neoplasien. Kombination mit 5-Fluoruracil.

15 patients with superficial basaliomas or premalignant epithelial neoplastic disorders (actinic keratosis, leukoplakia, Bowen's disease) were treated locally over three weeks with retinoic acid (RA) alone or in combination with 5-fluorouracil (5-FU). In 11 cases the lesions disappeared clinically, however, only 5 patients proved to be cured by histological examination. 4 of them were treated with RA combined with 5-FU. There was a decrease of the 3H-index after the first week and an increase after the third week of treatment. These findings suggest, that RA inhibits the proliferation of neoplastic keratinocytes and stimulates the proliferation of normal epidermal cells. Retinoic acid, therefore, has an inhibitory effect on epithelial neoplasias, particularly in combination with 5-FU. Since local therapy with RA and 5-FU is not sufficient for routine clinical purposes in all cases, their use should be restricted to selected patients.

[Which antibiotics are helpful in acne? A review of the literature and personal test results with minocyclin (klinomycin)]. / Welche Antibiotika helfen bei Akne? Eine Ubersicht der Literatur und eigene Prüfungsergebnisse mit Minocyclin (Klinomycin)

All tetracycline preparations seem to be systemically effective in acne. Quality and frequency of their side-effects, however, are different and should be carefully considered in each individual case. In an own study ninety-one patients treated with minocycline showed good response in 69% and moderate or no response in 31+. The main side-effects of the drug were nausea and giddiness, being of short duration in most cases. In patients with no response to a certain preparation change of the preparation may be helpful. Occasionally, acne does not respond to any tetracycline derivative. In these cases the use of non-tetracycline antibiotics, particularly of trimethoprim-sulphamethazol and lincomycines, is clearly effective. As a rule, we start treatment with tetracycline (500-750 mg/d) and reduce the dose to a minimum (ca. 100 mg/d), in order to withdraw the drug. In non-responsive cases another derivative and/or finally non-tetracycline antibiotics are administered for therapy.