Imine-enamine tautomerism—VI: C- vs n-alkylation of imines with electrophilic olefins

Recently described results concerning in particular the reaction between N-isopropylidene-cyclohexylamine 1b and methyl acrylate were reinvestigated, due to the claim that only N-alkylation takes place. Our results show that in fact several reactions do occur, particularly the C-alkylation yielding iminoesters 3b and 5, but that no N-alkylation takes place. The principal side reaction is the “aldolisation-crotonisation” of imine 1b which yields mesityl oxide imine 8 and cyclohexylamine which in turn adds on methyl acrylate to give β-aminoester 9.Enamine 4b which would have arisen by N-alkylation of imine 1b was independently prepared by enamination of acetone with secondary amine 9 and shown to spontaneously cyclize to enaminoketone 12, which compound was totally absent from the alkylation experiments. It is thus demonstrated that N-alkylation of imine 1b does not occur with methyl acrylate, not even reversibly.     

ELectron Collision Rates and Transport Coefficients of a Weakly Ionized dc Plasma in Ar/Sih4-Mixtures

The paper deals with electron kinetics of a Ar/SiH₄ dc plasma, using the stationary and spatially uniform Boltzmann equation. The solution of this kinetic equation has been obtained by applying higher order Legendre polynomial expansion of the electron velocity distribution. For varying mixture composition the energy distribution and relevant macroscopic quantities as mean energy, drift velocity, rate coefficients for excitation, dissociation and ionization and relevant energy transfer rates for these processes have been calculated. In particular, it has been found that a most effective activation of the feed gas occurs for SiH₄ admixtures in the range from 5 to 10 per cents.     

Photoénolisation—VIII: Stéréospécificitéet régiospécificitéde la réaction de diels-alder avec les photodiénols issus de la benzyl-2 et de l'éthyl-2 benz

Photoenols derived from 2-benzyl- and 2-ethylbenzophenone have been trapped by maleic anhydride, methyl fumarate and phenyl fumarate. Stereochemical determinations of the single adduct obtained in each case in high yield have shown unequivocally that the Diels-Alder addition proceeds from the (E,E)-dienol by an endo approach, an interaction between the dienol hydroxylic group and one of the dienophile carbonyl group being strongly determinant. These results do not eliminate the possibility that an unreactive (Z,E)-dienol be formed during the photochemical step.     

Artificial atoms can do more than atoms: deterministic single photon subtraction from arbitrary light fields

We study the interplay of photons interacting with an artificial atom in the presence of a controlled dephasing. Such artificial atoms consisting of several independent scatterers can exhibit remarkable properties superior to single atoms with a prominent example being a superatom based on Rydberg blockade. We demonstrate that the induced dephasing allows for the controlled absorption of a single photon from an arbitrary incoming probe field. This unique tool in photon-matter interaction opens a way for building novel quantum devices, and several potential applications such as a single photon transistor, high fidelity n-photon counters, or the creation of nonclassical states of light by photon subtraction are presented.     

Continuous loading of a conservative potential trap from an atomic beam

We demonstrate the fast accumulation of 52Cr atoms in a conservative potential from a guided atomic beam. Without laser cooling on a cycling transition, a dissipative step involving optical pumping allows us to load atoms at a rate of 2×10(7) s(-1) in the trap. Within less than 100 ms we reach the collisionally dense regime, from which we produce a Bose-Einstein condensate with subsequent evaporative cooling. This constitutes a new approach to degeneracy where Bose-Einstein condensation can be reached without a closed cycling transition, provided that a slow beam of particles can be produced.     

Nanolithography with metastabile helium

We have used a self-assembling monolayer of dodecanethiole molecules as the resist for a lithography technique based on a beam of metastable helium atoms. Doses as low as 3 metastable helium atoms per 10 molecules are enough to write patterns into this resist. An edge resolution of 30 nanometers is demonstrated. The writing mechanism is based on the damage of the resist due to Penning ionization.