Frozen shell approximation violation in negative ion formation from halogenated benzenes via dissociative attachment

A series of benzene derivatives (R(1)C(6)H(4)R(2)) has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), and PM3 quantum chemical calculations. The dissociation channel M(-.) --> Hal(-) + (M - Hal). is analysed from the point of view of symmetry conservation. Generally, a symmetry ban on dissociation may be avoided in at least two ways: (i) out-of-plane vibrations of the halogen atom in the molecular negative ion (MNI), mixing pi- and sigma-states of the anion; (ii) symmetrical in-plane vibration of the C-Hal bond, changing the order of the empty levels in the MNI with subsequent radiationless conversion into a sigma-state. Our analysis shows that neither of them provides a satisfactory explanation of the ECNI mass spectra for chlorobenzene, if one retains the usual assumption that an additional electron goes into the LUMO of the neutral molecule. Thus, it may be concluded that in this case electron capture causes a significant perturbation of the energy ordering of vacant orbitals, thus making the frozen shell approximation inapplicable. Copyright 2000 John Wiley & Sons, Ltd.     

Spectroradiometer for groundbased atmospheric ozone studies in the 2-mm-wavelength range

Conclusion A superheterodyne spectroradiometer for the 2-mm wavelength range suitable for atmospheric ozone observations has been described. Laboratory and field tests of the device have demonstrated its reliability and convenience for the important task of observing and reconstructing the vertical atmospheric ozone profile in inaccessible layers of the middle atmosphere. Further increase in the sensitivity of the device will be required.P. N. Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 5, pp. 546–555 May, 1990.     

Stability of atomic clocks based on entangled atoms

We analyze the effect of realistic noise sources for an atomic clock consisting of a local oscillator that is actively locked to a spin-squeezed (entangled) ensemble of N atoms. We show that the use of entangled states can lead to an improvement of the long-term stability of the clock when the measurement is limited by decoherence associated with instability of the local oscillator combined with fluctuations in the atomic ensemble's Bloch vector. Atomic states with a moderate degree of entanglement yield the maximal clock stability, resulting in an improvement that scales as N(1/6) compared to the atomic shot noise level.     

Manipulating light pulses via dynamically controlled photonic band gap

When a resonance associated with electromagnetically induced transparency in an atomic ensemble is modulated by an off-resonant standing light wave, a band of frequencies can appear for which light propagation is forbidden. We show that dynamic control of such a band gap can be used to coherently convert a propagating light pulse into a stationary excitation with nonvanishing photonic component. This can be accomplished with high efficiency and negligible noise even at the level of few-photon quantum fields thereby facilitating possible applications in quantum nonlinear optics and quantum information.     

Dynamic Interaction of Longitudinal and Transverse Laser-Induced Oscillations of a Rod

Doklady Physics - The problem of the interaction of longitudinal and transverse vibrations of a rod under thermal actions using laser radiation is considered. Simultaneously taking into account the...     

Diversity-oriented synthesis of N,N-dimethylamino-substituted azoles employing TBTU

A convenient, diversity-oriented approach for the transformation of readily available amidoximes, o-hydroxyarylamines, acyl hydrazines, carboximidohydrazides and thiohydrazides into their respective N,N-dimethylamino-substituted azoles is described. The method is particularly suitable for array chemistry application as it employs a stable, solid reagent TBTU.