Generalized Stern-Gerlach effect for chiral molecules

The Stern-Gerlach effect is well known as spin-dependent splitting of a beam of atoms with magnetic moments by a magnetic-field gradient. Here, we show that an induced gauge potential may lead to a similar effect for chiral molecules. In the presence of three inhomogeneous light fields, the center of mass of a three-level chiral molecule is subject to an optically induced gauge potential, and the internal dynamics of the molecule can be described as an adiabatic evolution in the reduced pseudospin subspace of the two lowest energy levels. We demonstrate numerically that such an induced gauge potential can lead to observable pseudospin-dependent and chirality-dependent generalized Stern-Gerlach effects for mixed left- and right-handed chiral molecules under realistic conditions.     

Longitudinal Stern-Gerlach effect for slow cesium atoms

The mechanical Stern-Gerlach effect is investigated in the case of a slow atomic cloud falling through an inhomogeneous magnetic field featuring a strong longitudinal gradient. The resulting Zeeman sublevel state selection is demonstrated under various experimental conditions. Longitudinal spatial separations are in agreement with numerical simulations that take into account the gravitational acceleration and both the transverse and axial magnetic forces. Since separations greater than 20 cm are obtained, potential applications in atom optics are outlined. Received: 16 February 1998 / Received in final form: 1 April 1998 / Accepted: 6 April 1998     

Spin State Determination Using a Stern-Gerlach Device

The well-known Stern-Gerlach device is proposed here for determination of a particle spin state instead of using it for measurement of spin observables. It is shown that measurement of particle momentum distributions (before and after the action of the device magnetic field) allows one to determine the particle initial spin state in the case of an arbitrary spin value. It is demonstrated that one cannot use for this purpose the usual treatment of the Stern-Gerlach experiment based on the entanglement of spin and spatial states.     

Quantum-mechanical analysis of pulse reconstruction for a narrow bandwidth attosecond x-ray pulse

The photoelectron energy spectra (PESs) excited by narrow bandwidth attosecond x-ray pulses in the presence of a few-cycle laser are quantum-mechanically calculated. Transfer equations are used to reconstruct the detailed temporal structure of an attosecond x-ray pulse directly from a measured PES. Theoretical analysis shows that the temporal uncertainties of the pulse reconstruction depend on the x-ray bandwidth. The procedure of pulse reconstruction is direct and simple without making any previous pulse assumption, data fitting analysis and time-resolved measurement of PESs. The temporal measurement range is half of a laser optical cycle.     

Stern-Gerlach studies of organometallic sandwich clusters

Stern-Gerlach type magnetic deflection measurements were performed for two types of multiple sandwich clusters: vanadium-benzene V_n(C₆H₆)_n+1 and terbium-cyclooctatetraene Tb_n(C₈H₈)_n+1. Beams of V_n(C₆H₆)_n+1 clusters (n = 1-4) showed symmetric broadening induced by the inhomogeneous field, indicating free spin behavior similar to that displayed by isolated paramagnetic atoms. By contrast, beams of Tb_n(C₈H₈)_n+1 clusters displayed one-sided deflection, indicating that fast spin relaxation occurs within the clusters. The difference in the magnetic deflection behavior exhibited by these two systems is explained by their electronic structures, specifically the bonding characteristics between metal atoms and ligand molecules.     

Quantum-mechanical effects in a linear time-dependent potential

The solution of the time-dependent Schrödinger equation is discussed fora particle confined in half-space x>0 with a linear potential V(x)=Kx in the following situations:(a) sudden removal of the wall and switching on the linear potential V(x)=Kx at x ≤0,(b) sudden removal of the wall and the potential and(c) sudden removal of the potential.A brief discussion of quantum statistics is presented.     

Quantum-mechanical calculations and analysis of vibrational modes in lead magnoniobate

The vibrational modes in lead magnoniobate have been calculated using the frozen phonon method. It has been shown that lead atoms participate in two radically different vibrational modes, namely, a nonpolar antiferrodistortive mode, which involves the antiphase motion of some lead atoms with respect to other lead atoms, and a polar mode, which includes the polar motion of lead atoms with respect to other atoms of the lattice. The nontrivial properties of lead magnoniobate have been discussed in terms of the unity and conflict of these modes.     

Quantum-mechanical oscillator in a uniform force field

The symmetry group of an isotropic oscillator explaining additional degeneracy of its energy levels was for the first time considered by Demkov [1–3]. He directed attention to the fact that harmonic oscillator Hamiltonian symmetry was beyond the scope of usual geometric concepts and could be expressed using canonical transformations relating coordinates and momenta. We show in this paper how the symmetry properties of the harmonic oscillator Hamiltonian can be used to solve the dynamic problem of an oscillator in a uniform force field.     

Quantum-mechanical analysis of resonance Raman scattering spectra of the uracil molecule

A direct quantum-mechanical calculation of the relative intensities of lines in the resonance Raman scattering (RRS) spectra of uracil is performed by a method developed earlier by the authors on the basis of the adiabatic model in the Herzberg-Teller approximation [1]. It is shown that the main regularities in the intensity distribution of spectra can be explained only by taking into account the vibronic mixing of electronic states and the contribution to the scattering tensor components from the excited electronic states adjacent to the resonance state. The calculated results are in satisfactory agreement with the results of experimental studies of the RRS spectra of uracil excited by laser radiation at 266, 240, 218, and 200 nm.     

On the theory of the Stern-Gerlach apparatus

We present, in various limits, analytical expressions for the center-of-mass wave function of a spin-1/2 atom as it is deflected by a Stern-Gerlach apparatus.Work Supported by the Office of Naval Research.     

Magneto-optical longitudinal Kerr effect in a film-substrate system

The problem of electromagnetic reflection at an arbitrary angle of incidence in a system consisting of an isotropic ambient, a magnetic film and a thick magnetic substrate is considered. The magnetization in both the film and substrate is assumed parallel to the planar interfaces and to the plane of incidence. The analysis provides the dispersion relation for the guided wave propagation in the system. The obtained general formulae are applied to the special cases of (a) normal incidence, (b) oblique incidence on a uniaxial film on a uniaxial substrate, both optical axes being parallel to the interfaces and to the plane of incidence, and (c) to the case when the permittivity tensor diagonal elements are the same and the off-diagonal element is small. The possible practical applications of the present analysis are in the ellipsometry of thin-film — substrate structures displaying magnetic order and in the theory of magneto-optic thin-film devices for integrated optics.     

Quantum-mechanical investigation of field-emission mechanism of a micrometer-long single-walled carbon nanotube

A quantum-mechanical simulation is carried out to investigate the charge distribution and electrostatic potential along a 1 microm long (5,5) single-walled carbon nanotube under realistic field-emission experimental conditions. A single layer of carbon atoms is found sufficient to shield most of the electric field except at the tip where strong field penetration occurs. The penetration leads to a nonlinear decrease of potential barrier for emission, which is equally responsible for the low threshold voltage besides the well-known geometrical field enhancement factor.