Newsfeeds
Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers
Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics
-
Dynamics of highly-ionized diiodomethane: Coulomb explosion, energy exchange and rotating fragments
The dissociation dynamics of diiodomethane molecules (CH2I2) have been investigated following absorption of 98 eV XUV photons. In the measurement at the reaction microscope endstation at the free-electron laser FLASH2, ionic fragments created by 4d core ionization followed by Auger decay have been detected in coincidence. In the one-photon absorption channel CH2+/I+/I+, a concerted three-ion breakup and a sequential dissociation via a rotating intermediate CH2I2+ ion have been identified. Classical simulations based on a Coulomb repulsion model and ab initio molecular dynamics in the frame of the Density Functional Theory have been performed. Both types of simulations reproduce different aspects of the observed fragmentation dynamics, in particular a delayed second bond break after dissociation of the first iodine ion. In the study of the potential energy surface we have located a minimum after the emission of the first I+. We attribute the sequential mechanism to the trapping of the rotationally excited CH2I2+ fragment in this transient intermediate, which corresponds to a potential energy well that protects it against the cleavage of the second C–I bond.
-
Nonclassical states of light induced via measurement in a bimodal system
We investigate generation of nonclassical photon states via conditional measurement process in a two mode coupled waveguide. Interaction of the fields takes place in a waveguide beamsplitter due to the overlap between normal modes supported therein. A quadratic Hamiltonian of two degrees of freedom describes the hopping interaction. An initial two mode squeezed state undergoes a unitary evolution governed by the interaction Hamiltonian for a specified time. Following this the bipartite state is subjected to a projective measurement that detects nth Fock state in one subsystem. The post-measurement excitation rendered in the residual subsystem depends on the prior time of interaction between the modes as well as the interaction strength. The Wigner quasiprobability distribution of an arbitrary post-selection state is computed. Its nonclassicality is examined via the negativity of the Wigner distribution. The sub-Poissonian nature of the photon statistics is revealed by the Mandel parameter. The dynamically generated squeezing is evidenced in the post-measurement state. In the ultrastrong coupling regime the parity even and odd states display markedly different nonclassical properties. The nonclassicality of the post-measurement states obtained here may be controlled by varying the interaction strength and the time span of interaction between the modes.
-
Investigations of electron removal processes in slow He2+- and He+-Ne2 collisions and of their implications for the subsequent dimer fragmentation through interatomic Coulombic decay
We implement an independent-atom and independent-electron model to investigate the collision systems of He2+ and He+ ion projectiles impinging on a neon dimer target. The dimer is set to be stationary at its equilibrium bond length with the projectile traveling parallel to the dimer axis at a speed corresponding to the collision energy of 10 keV amu−1. Two approaches, namely multinomial and determinantal, are used as an analysis of these collisions. Each of the analyses is broken down into two types of models that do not and do include a change in the projectile charge state due to electron capture from the dimer. All calculations are performed using both a frozen atomic target and a dynamic response model using the coupled-channel two-center basis generator method for orbital propagation. All one-electron and two-electron removal processes are calculated, though particular attention is paid to those that result in the Ne+-Ne+ fragmentation channel due to its association with interatomic Coulombic decay (ICD). For He2+ impact, we find that Ne(2s) electron removal is strong across all analyses and models, which is in line with previous results that show that ICD contributes to dimer fragmentation through that channel. We also find indications that there is a pure ICD yield when utilizing a He+ projectile and applying the model that takes into account the change in projectile charge state.
-
On the high-momentum oscillatory distribution and related quantum information theoretical measures of confined alkali systems (H, Li)
The effect of impenetrable spherical confinement on alkali systems (H, Li) has been thoroughly examined, emphasizing the distinctive high-momentum oscillatory behavior of the momentum space radial density. We have utilized the Ritz variational framework with a Slater-type basis set to derive the position-space wavefunction and Fourier–Dirac transformation of the former to find the momentum-space wavefunction, analytically. The derived momentum-space density has been analyzed in four asymptotic limits ( , , , and ; R being the confinement radius and p being the radial component of linear momentum) and its oscillatory behavior in strong spatial confinement region is critically investigated. Oscillatory behavior is also noticed in the Compton profile of the compressed atomic system. Furthermore, the effects of confinement on Shannon information entropy in both position and momentum spaces are investigated, offering insights into the Bialynicki–Birula–Mycielski inequality and the local variations of information measures in terms of Shannon entropy density.
- Special issue on experimental and theoretical extreme ultraviolet to x-ray non-linear methods