Search results for "Rotational energy"
showing 10 items of 35 documents
How important is roaming in the photodegradation of nitrobenzene?
2020
At low excitation energies nitrobenzene photoreleases NO with low translational and rotational energy, while at higher excitation energies NO is photoreleased with both low and high translational and rotational energy. The fast products are formed through a singlet-triplet crossing (STC) region featuring an oxaziridine ring, while a ground state roaming mechanism was suggested to produce the slow molecules. Computing translational and rotational energies performing CASSCF classical dynamics, we here prove how the same oxaziridine STC can account for both fast and slow photoproducts, depending on the region of the seam through which the ground state is populated. A roaming-type STC/CI has al…
United Atom Force Field for Molecular Dynamics Simulations of 1,4-Polybutadiene Based on Quantum Chemistry Calculations on Model Molecules
1998
We present a united atom force field for simulations of 1,4-polybutadiene based on ab initio quantum chemistry calculations on model molecules. The geometries and energies of conformers and rotational energy barriers in model alkenes and dienes have been determined from high-level quantum chemistry calculations. A rotational isomeric state (RIS) model for 1,4-polybutadiene based on the conformer geometries and energies of the model molecules has been derived. The characteristic ratio and its temperature dependence for cis-1,4-polybutadiene and trans-1,4-polybutadiene, and the characteristic ratio of a random copolymer of cis and trans units, as predicted by the RIS model, are in good agreem…
On the Optical Counterpart of SAX J1808.4-3658 during Quiescence: Evidence for an Active Radio Pulsar?
2003
The optical counterpart of the binary millisecond X-ray pulsar SAX J1808.4-3658 during quiescence was detected at V =21.5 mag, inconsistent with intrinsic emission from the faint companion star. We propose that the optical emission from this system during quiescence is due to the reprocessing by the companion star and a remnant accretion disk of the rotational energy released by the fast spinning neutron star, switched on, as magneto-dipole rotator (radio pulsar), during quiescence. In this scenario the companion behaves as a bolometer, reprocessing in optical the intercepted fraction of the power emitted by the pulsar. This reprocessed fraction depends only on known binary parameters. Thus…
Stadnik and Flambaum Reply:
2016
In the comment of Avelino, Sousa and Lobo [arXiv:1506.06028], it is argued, by comparing the kinetic energy of a topological defect with the overall energy of a pulsar, that the origin of the pulsar glitch phenomenon due to the passage of networks of topological defects through pulsars is faced with serious difficulties. Here, we point out that topological defects may trigger pulsar glitches within traditional scenarios, such as vortex unpinning. If the energy transfer from a topological defect exceeds the activation energy for a single pinned vortex, this may lead to an avalanche of unpinning of vortices and consequently a pulsar glitch, and therefore the source of angular momentum and ene…
On the maximum efficiency of the propeller mass-ejection mechanism
2007
Aims. We derive simple estimates of the maximum efficiency with which matter can be ejected by the propeller mechanism in disk-fed, rotating magnetic neutron stars. Some binary evolution scenarios envisage that this mechanism is responsible for expelling to infinity the mass inflowing at a low rate from the companion star, therefore limiting the total amount of mass that can be accreted by the neutron star. Methods. We demonstrate that, for typical neutron star parameters, a maximum of ��_{pro} < 5.7 (P_{-3})^{1/3} times more matter than accreted can be expelled through the propeller mechanism at the expenses of the neutron star rotational energy (P_{-3} is the NS spin period in unit of …
Analysis of the "Unusual" Vibrational Components of Triply Degenerate Vibrational Mode nu(6) of Mo(CO)(6) Based on the Classical Interpretation of th…
2001
Rotational structure of the triply degenerate vibrational state nu(6)(F(1u)) of the octahedral molecule Mo(CO)(6) is analyzed qualitatively on the basis of classical mechanics. We show that the energy level redistribution between the vibrational components of nu(6)(F(1u)) occurs due to rotational excitation and is related to the formation of singular points of classical rotational energy surfaces. The singularity is stable under small variations of parameters of the effective rovibrational Hamiltonian. Parameters responsible for the persistence of this phenomenon are specified. Comparison with quantum calculations demonstrates the high qualitative and quantitative accuracy of our classical …
Which Reaches the Bottom First?
2008
A well-known classroom demonstration involves the rolling of hollow and solid objects down an incline.1 The fact that the objects roll at different rates can be used as a starting point in introducing students to rotational dynamics and rotational kinetic energy. In this paper we describe a simple quantitative version of the demonstration that is suitable for use as a laboratory experiment.
AMR simulations of the low bar-mode instability of neutron stars
2007
It has been recently argued through numerical work that rotating stars with a high degree of differential rotation are dynamically unstable against bar-mode deformation, even for values of the ratio of rotational kinetic energy to gravitational potential energy as low as O(0.01). This may have implications for gravitational wave astronomy in high-frequency sources such as core collapse supernovae. In this paper we present high-resolution simulations, performed with an adaptive mesh refinement hydrodynamics code, of such low T/|W| bar-mode instability. The complex morphological features involved in the nonlinear dynamics of the instability are revealed in our simulations, which show that the…
Angular Energy Distribution of Collapsar-Jets
2008
Collapsars are fast-spinning, massive stars, whose core collapse liberates an energy, that can be channeled in the form of ultrarelativistic jets. These jets transport the energy from the collapsed core to large distances, where it is dissipated in the form of long-duration gamma-ray bursts. In this paper we study the dynamics of ultrarelativistic jets produced in collapsars. Also we extrapolate our results to infer the angular energy distribution of the produced outflows in the afterglow phase. Our main focus is to look for global energetical properties which can be imprinted by the different structure of different progenitor stars. Thus, we employ a number of pre-supernova, stellar models…
Mechanical energy states during running.
1978
Changes in total mechanical work and its partitioning into different energy states (kinetic, potential and rotational) during a step cycle of running were investigated on six well trained athletes who ran at the test speeds of 40, 60, 80, and 100% (9.3 +/- 0.3 m/s) of maximum. Cinematographic techniques were utilized to calculate the mechanical energy states as described by Norman et al. (1976), using a 13 segment mechanical model of a runner as the basis for the computations. The data showed that both the kinetic and rotational energy increased parabolically but the potential energy decreased linearly with increases in running velocity. The calculated power of the positive work phase incre…