Probing time-dependent molecular dipoles on the attosecond time scale

Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N(2), CO(2), and C(2)H(4)), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.

Probing single-photon ionization on the attosecond time scale

We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s(2) and from the 3p(6) shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

Attosecond electron spectroscopy using a novel interferometric pump-probe technique

We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse (AP) with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original AP. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multipath interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the AP duration.

Phase measurement of resonant two-photon ionization in helium

We study resonant two-color two-photon ionization of helium via the 1s3p (1)P(1) state. The first color is the 15th harmonic of a tunable Ti:sapphire laser, while the second color is the fundamental laser radiation. Our method uses phase-locked high-order harmonics to determine the phase of the two-photon process by interferometry. The measurement of the two-photon ionization phase variation as a function of detuning from the resonance and intensity of the dressing field allows us to determine the intensity dependence of the transition energy.

Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

Midazolam combined with paracervical blockade compared to general anaesthesia for curettage of the uterus

Two anaesthetic techniques were compared in a randomized trial of 60 ASA I and II women admitted for diagnostic dilatation and curettage of the uterus. Group I had fentanyl 2.5 micrograms/kg and thiopentone 2 mg/kg i.v. Supplementary thiopentone 50 mg was given every 15 s until loss of the eyelid reflex. Anaesthesia was maintained with nitrous oxide in oxygen 2/1 together with supplementary thiopentone 50 mg as required. Group II had midazolam 0.1 mg/kg i.v. and a supplementary 0.025 mg/kg every second min until sleep or dysarthria, followed by paracervical blockade with 1% mepivacaine 10 ml on each side of the portio. There was no significant depression of the cardiovascular system. The working conditions for the gynaecologist were good in both groups. The midazolam technique gave just as good amnesia as did general anaesthesia, and there was a high degree of patient satisfaction in both groups. In the thiopentone group there was a significant depression of the respiratory rate and a significantly higher frequency of adverse effects (nausea and vomiting) as compared to the midazolam group. It is concluded that paracervical blockade combined with midazolam, titrated i.v., until sleep or dysarthria, is a recommendable anaesthetic technique for diagnostic dilatation and curettage.

Candida chorioamnionitis and intra-uterine contraceptive device

In spite of the very common occurrence of vaginal candidiasis in pregnant women (1), the uterus is seldom affected. There are few reports in the literature of intrauterine infection. The present paper presents a case of placental and fetal candidiasis in association with the presence of an intra-uterine contraceptive device (IUD).

The course of pregnancy following spontaneous abortion

With the aim of being able to advise women concerning a recommended interval between spontaneous abortion and a new pregnancy, the course of pregnancies following spontaneous abortion was studied. Nineteen women conceived within the first 12 weeks. There were no abortions, and 18 pregnancies proceeded normally. Thirty women conceived between 12 and 26 weeks, 29 pregnancies proceeded normally, and none aborted. Forty-two women conceived later than 26 weeks after the abortion. Seven pregnancies terminated in abortion, and 30 proceeded normally. We found no reason to advise women to postpone a new conception after spontaneous abortion.