Search results for " molecule"
showing 10 items of 1523 documents
Analogue of oscillation theorem for nonadiabatic diatomic states: application to the A 1Σ+ and b 3Π states of KCs
2010
Relative intensity measurements in the high resolution A (1)Sigma(+) approximately b (3)Pi--X (1)Sigma(+) laser induced fluorescence spectra of the KCs molecule highlighted a breakdown of the conventional one-dimensional oscillation theorem (L. D. Landau and E. M. Lifshitz, Quantum Mechanics, Pergamon, New York, 1965). For strongly spin-orbit coupled A (1)Sigma(+) and b (3)Pi states the number of nodes n(A) and n(b) of the non-adiabatic vibrational eigenfunctions phi and phi corresponding to the v-th eigenstate differs essentially from their adiabatic counterparts. It is found, however, that in the general case of two-component states with wavefunctions phi and phi coupled by the sign-const…
Soft X-Ray Irradiation of Methanol Ice: Implication for H2CO Formation in Interstellar Regions
2010
We performed 0.3 keV soft X-ray irradiation of a methanol ice at 8 K under ultra-high vacuum conditions. To the best of our knowledge, this is the first time that soft X-rays are used to study photolysis of ice analogs. Despite the low irradiation dose of 10{sup -6} photons molecule{sup -1}, the formation of formaldehyde has been observed. The results of our experiments suggest that X-rays may be a promising candidate to the formation of complex molecules in regions where UV radiation is severely inhibited.
Probing fast oscillating scalar dark matter with atoms and molecules
2021
Light scalar Dark Matter with scalar couplings to matter is expected within several scenarios to induce variations in the fundamental constants of nature. Such variations can be searched for, among other ways, via atomic spectroscopy. Sensitive atomic observables arise primarily due to possible changes in the fine-structure constant or the electron mass. Most of the searches to date have focused on slow variations of the constants (i.e. modulation frequencies $<$ 1 Hz). In a recent experiment \mbox{[Phys. Rev. Lett. 123, 141102 (2019)]} called WReSL (Weekend Relaxion-Search Laboratory), we reported on a direct search for rapid variations in the radio-frequency band. Such a search is particu…
Influence effect of an external electric field and dissipative tunneling on intracenter optical transitions in quantum molecules with D2- states
2020
In the zero-range potential model and in the effective mass approximation, dispersion equations have been obtained, that describe dependence of the average binding energies of the quasistationary g- and u-states of the D − 2 - center in the QD, as well as the widths of energy levels on the magnitude of the external electric field and the parameters of 1D-dissipative tunneling. Dips in the field dependences of the binding energies average values for quasi-stationary g- and u-states have been revealed. It is shown that the field dependences of the energy level widths for the g- and u- states of the D − 2 -center have a resonance structure at the external electric field strengths corresponding…
Polarization of high harmonic generated spectra in H+2ion
2013
AbstractWe study the polarization of the harmonics generated by a homonuclear diatomic molecule in the presence of an intense, linearly polarized laser field. The polarization parameters of the emitted radiation are investigated as a function of the angle between the laser electric field and the molecular axis. The calculations are carried out by assuming a single active electron model with fixed nuclei; a two-dimensional model of the system is used. We find a different dependence of the parameters of the harmonics vs in the first or second half of the emitted spectrum. In particular, the differences are accentuated for , while for higher angles, until the perpendicular orientation, almost …
Ionization dynamics of a model molecular ion
2005
We study the ionization dynamics of a model one-dimensional molecular ion as a function of the internuclear distance R, for different values of the laser intensity. The electron–nucleus potential is assumed to be a Poschl–Teller potential, whose parameters are chosen to have only two bare bound molecular states in the range of R considered. We describe three different theoretical approaches to study the dynamics of the system: an exact numerical, a semiperturbative and a phenomenological approach. All these approaches indicate the presence of a sharp ionization peak for a critical value of the internuclear distance, for which the energy difference between the two bound levels coincides with…
Neutron scattering and molecular correlations in a supercooled liquid
1999
We show that the intermediate scattering function $S_n(q,t)$ for neutron scattering (ns) can be expanded naturely with respect to a set of molecular correlation functions that give a complete description of the translational and orientational two-point correlations in the liquid. The general properties of this expansion are discussed with special focus on the $q$-dependence and hints for a (partial) determination of the molecular correlation functions from neutron scattering results are given. The resulting representation of the static structure factor $S_n(q)$ is studied in detail for a model system using data from a molecular dynamics simulation of a supercooled liquid of rigid diatomic m…
Test of mode coupling theory for a supercooled liquid of diatomic molecules. II.q-dependent orientational correlators
1997
Using molecular dynamics computer simulations we study the dynamics of a molecular liquid by means of a general class of time-dependent correlators S_{ll'}^m(q,t) which explicitly involve translational (TDOF) and orientational degrees of freedom (ODOF). The system is composed of rigid, linear molecules with Lennard- Jones interactions. The q-dependence of the static correlators S_{ll'}^m(q) strongly depend on l, l' and m. The time dependent correlators are calculated for l=l'. A thorough test of the predictions of mode coupling theory (MCT) is performed for S_{ll}^m(q,t) and its self part S_{ll}^{(s)m}(q,t), for l=1,..,6. We find a clear signature for the existence of a single temperature T…
Test of mode coupling theory for a supercooled liquid of diatomic molecules.I. Translational degrees of freedom
1997
A molecular dynamics simulation is performed for a supercooled liquid of rigid diatomic molecules. The time-dependent self and collective density correlators of the molecular centers of mass are determined and compared with the predictions of the ideal mode coupling theory (MCT) for simple liquids. This is done in real as well as in momentum space. One of the main results is the existence of a unique transition temperature T_c, where the dynamics crosses over from an ergodic to a quasi-nonergodic behavior. The value for T_c agrees with that found earlier for the orientational dynamics within the error bars. In the beta- regime of MCT the factorization of space- and time dependence is satisf…
Rotational-vibrational relative equilibria and the structure of quantum energy spectrum of the tetrahedral molecule P4
2001
We find relative equilibria (RE) of the rotating and vibrating tetrahedral molecule P4 and study the correspondence of these RE's to the extremal quantum states in the vibration-rotation multiplet and to the extrema of the semi-quantum rotational energy surfaces obtained for a number of excited vibrational states. To compute the energy of RE's we normalize the full rotation-vibration Hamiltonian H of P4 in the approximation of nonresonant modes ν E 2 and ν F_2 3 and find the stationary points of the resulting normal form (known as reduced effective Hamiltonian H eff ) which is defined on the reduced phase space CP 2 × CP 1 × S 2 . Most of these points are fixed points of the symmetry group …