Search results for "Ham"
showing 10 items of 2612 documents
Simultaneous Analysis of the ν2 Raman and ν2 + ν6 Infrared Spectra of the SF6 Molecule
2001
High-resolution Raman spectra of the nu(2) band of SF(6) have been recorded at a temperature of 195 K (dry ice) and a pressure of 39 mbar. These spectra were analyzed using a new set of programs specially written for XY(6) molecules. These programs, called HTDS (highly spherical top data system) in reference to the set of programs called STDS (spherical top data system written for XY(4) molecules) can be freely accessible through ftp (user anonymous) at jupiter.u-bourgogne.fr or on the web at the URL http://www.u-bourgogne.fr/LPUB/shTDS.html. The study of nu(2) was made using a Hamiltonian developed through the third order. Four parameters were determined. The standard deviation obtained us…
Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brachytherapy dosimetry
2015
Purpose: A surface electronic brachytherapy (EBT) device is in fact an x-ray source collimated with specific applicators. Low-energy (<100 kVp) x-ray beam dosimetry faces several challenges that need to be addressed. A number of calibration protocols have been published for x-ray beam dosimetry. The media in which measurements are performed are the fundamental difference between them. The aim of this study was to evaluate the surface dose rate of a low-energy x-ray source with small field applicators using different calibration standards and different small-volume ionization chambers, comparing the values and uncertainties of each methodology. Methods: The surface dose rate of the EBT unit …
Piecewise static Hamiltonian for an atom in strong laser field
2009
We show that it is possible to use a piecewise constant Hamiltonian to describe the main features of the dynamics of an atom interacting with a laser field. In particular we show that using this approximation we are able to give a good description of the ionization signal, of the HHG spectra and of the attosecond pulses generated by the radiating electron. Finally, we give an explicit formula to evaluate the ionization rate in the time dependent laser field. This formula, which is a generalization of the Landau formula for the ionization rate of an atom in a static electric field, fairly well reproduces the numerical ionization rates for a broad range of laser frequency and intensity. The m…
The local group K(4) in the algebraic approach to vibrational spectra of tetrahedral molecules: Application to silane
1992
Abstract In a previous paper, Michelot and Moret-Bailly (J. Phys., 48, 51 (1987)) proposed an algebraic treatment of vibrational stretching modes in polyatomic molecules. They used the properties of the group chain U(p + 1) ⊃ U(p) ⊃ S(p) ⊃ G for the study of p identical oscillators. The molecule, with p equivalent bonds described as a system of p oscillators, has a symmetry group G. We develop in this paper an application to p = 4 equivalent oscillators. We show that, for a tetrahedral molecule, the group chain U(5) ⊃ U(4) ⊃ S(4) ≈ Td can be completed, in a local point of view, with a particular group K(4): U(5) ⊃ U(4) ⊃ K(4) ⊃ S(4) ≈ T d This group provides us with available labels which c…
Forward-central two-particle correlations in p–Pb collisions at sNN=5.02 TeV
2016
Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 < |η| < 4.0) and associated particles in the cen
Quantum Sensors Assisted by Spontaneous Symmetry Breaking for Detecting Very Small Forces
2015
We propose a quantum-sensing scheme for measuring weak forces based on a symmetry-breaking adiabatic transition in the quantum Rabi model. We show that the system described by the Rabi Hamiltonian can serve as a sensor for extremely weak forces with sensitivity beyond the yoctonewton (yN) per sqrt (Hz) range. We propose an implementation of this sensing protocol using a single trapped ion. A major advantage of our scheme is that the force detection is performed by projective measurement of the population of the spin states at the end of the transition, instead of the far slower phonon number measurement used hitherto.
Population dynamics based on ladder bosonic operators
2021
Abstract We adopt an operatorial method, based on truncated bosons, to describe the dynamics of populations in a closed region with a non trivial topology. The main operator that includes the various mechanisms and interactions between the populations is the Hamiltonian, constructed with the density and transport operators. The whole evolution is derived from the Schrodinger equation, and the densities of the populations are retrieved from the normalized expected values of the density operators. We show that this approach is suitable for applications in very large domain, solving the computational issues that typically occur when using an Hamiltonian based on fermionic ladder operators.
Chaos and nonlinearities in high harmonic generation
2016
Linearity is a fundamental postulate of quantum mechanics which is occasionally the subject of debate. This paper investigates the possibility of checking this assumption by using a laser field. We study the corrections caused by the presence of a small nonlinearity in the Hamiltonian of a quantum system. As a model we use a simplified two-level quantum system whose states are coupled by a small off-diagonal term proportional to the population of the upper level. The nonlinearity causes spontaneous decay of the upper level, shift and broadening of the line and the sensitive dependence of the final state on the initial condition. The presence of a strong laser field, resonant with the atomic…
A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests.
2012
In this work we present the design, characterization and first clinical tests of an in-house developed two-dimensional liquid-filled ionization chamber prototype for the verification of small radiotherapy fields and treatments containing such small fields as in radiosurgery, which consists of 2 mm × 2 mm pixels arranged on a 16×8 rectangular grid. The ionization medium is isooctane. The characterization of the device included the study of depth, field-size and dose-rate dependences, which are sufficiently moderate for a good operation at therapy radiation levels. However, the detector presents an important anisotropic response, up to ≃ 12% for front versus near-lateral incidence, which can …
�ber die Stabilit�t periodischer L�sungen bei zeitabh�ngigen Hamiltonschen Differentialgleichungen von einem Freiheitsgrad
1987
The preservation of certain stable period solutions of the harmonic oscillator under small time-dependent, non-isochronous, and Hamiltonian perturbations is proved.