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1.
Damping width of the double giant dipole resonance of136Xe excited in relativistic heavy ion collisions is calculated by diagonalizing a microscopic Hamiltonian in a basis containing one-, two- and three-phonon states. The coupling between these states is determined making use of the fermion structure of the phonons. The resulting width of the double giant dipole resonance is close to √2 times the width of the single giant dipole resonance.  相似文献   

2.
An irreducible vector operator is used to generate isovector monopole states with welldefined values of T and Tz in N > Z nuclei. Reduced transition strengths are calculated in two different ways and the results seem compatible. The Wigner-Eckart theorem is used to derive expressions for the mixing of the monopole states with the ground state and its analog states. Expressions for the escape widths of the monopole states are also derived. An application is made to double analog resonances, and it is found, contrary to expectations, that the mixing with the T?1 monopole state is unable to account for the observed elastic partial width of these resonances in medium and heavy nuclei. The reason for this is the small escape width of the monopole state.  相似文献   

3.
A method to get both upper and lower bounds on real and imaginary parts of resonance eigenvalues is extended to Schrödinger operators with exterior dilation analytic potential. We apply it to a simple model potential where the bound states and resonances are exactly known.  相似文献   

4.
《Nuclear Physics A》1998,641(1):95-106
The damping width γGDR of the giant dipole resonance, due to its coupling to doorway states, is studied within the framework of the thermal Green's functions theory. It is found that γGDR reflects the temperature dependence of the single-particle damping width but, as a consequence of the cancellation effects between self-energy and vertex contributions, the coefficient of such a dependence is so small that it can essentially be neglected, within the temperature range of physical interest.  相似文献   

5.
The decay width of higher multipole giant resonances is described within the framework of the newly developed Fourier-Bessel random-phase approximation. We calculate the distribution of the isoscalar and isovector multipole strength for electric resonances up to Jπ = 7 ?. In our model we find no concentrated multipole strength beyond the hexadecapole.  相似文献   

6.
《Nuclear Physics A》1986,458(2):301-336
We derive a theory for small amplitude motion about states in thermal equilibrium. This motion couples mean-field oscillations and occupation number relaxations. The theory contains the effects of two-body collisions treated beyond the Markov approximation. The damping of collective modes is studied in a stochastic two-level model. The widths of giant resonances in finite nuclei are estimated using sum rules.  相似文献   

7.
The low-lying 3? and 5? collective modes seem to play a central role in the damping width of the giant resonances. The possibility of observing these couplings is suggested.  相似文献   

8.
We prove that the Schrödinger operator –d 2/dx2+Fx+W(x) onL 2(R) withW bounded and analytic in a strip has no resonances in a region ImE–exp(–C/F).  相似文献   

9.
We implement the Brink–Axel hypothesis for the excitation of the double giant dipole resonance (DGDR): the background states which couple to the one-phonon giant dipole resonance are themselves capable of dipole absorption. These states (and the ones which couple to the two-phonon resonance) are described in terms of the gaussian orthogonal ensemble of random matrices. We use second-order time-dependent perturbation theory and calculate analytically the ensemble-averaged cross section for excitation of the DGDR. Numerical calculations illuminate the mechanism and the dependence of the cross section on the various parameters of the theory, and are specifically performed for the reaction 208Pb + 208Pb at a projectile energy of 640 MeV/nucleon. We show that the contribution of the background states to the excitation of the DGDR is significant. We find that the width of the DGDR, the energy-integrated cross section and the ratio of this quantity over the energy-integrated cross section for the single giant dipole resonance, all agree with experiment within experimental errors. We compare our approach with that of Carlson et al. who have used a similar physical picture.  相似文献   

10.
11.
We prove a lower bound for the width of Stark resonances in one dimension.  相似文献   

12.
Isoscalar monopole vibrations in spherical nuclei are studied within the Landau-Vlasov dynamics. Energy and strength of the giant monopole resonance (GMR) are well reproduced. The Landau damping of the monopole vibrations is analyzed. It is found that the local Fermi surface corresponding to the GMR is deformed. The collision integral is included within the relaxation time approximation. The found total width is too small to explain the observed one in heavy nuclei. Because the Landau damping is sensitive to the effective nuclear force the missing part of the width can be connected to certain properties of the latter.  相似文献   

13.
14.
A sharp intense sub-Doppler feature is predicted in the probe absorption spectrum of an atomic four-level system when a hyperfine-split state interacts with a single pump. The sub-Doppler feature, which is flanked by two power-broadened transparency windows, is obtained when the frequency of the pump is greater than that of the probe, and the residual Doppler broadening is significant.  相似文献   

15.
It is shown that the RPA plus perturbation approach which is commonly used to calculate microscopically the spreading width of Giant Resonances is equivalent to Landau's suggestion that the damping width of zero sound at temperatureT=0 can be obtained by multiplying the classical collision result with an energyω- andT-dependent correction factor [1+(ω/2πkT)2] withT→0.  相似文献   

16.
17.
We study the dynamics near the intersection of a weaker and a stronger resonance inn-degree-of-freedom, nearly integrable Hamiltonian systems. For a truncated normal form we show the existence of (n–2)-dimensional hyperbolic invariant tori whose whiskers intersect inmultipulse homoclinic orbits with large splitting angles. The homoclinic obits are doubly asymptotic to solutions that diffuse across the weak resonance along the strong resonance. We derive a universalhomoclinic tree that describes the bifurcations of these orbits, which are shown to survive in the full normal form. We illustrate our results on a three-degree-of-freedom mechanical system.  相似文献   

18.
《Physics letters. A》1987,121(1):25-28
Short wavelength electrostatic perturbations in one-dimensional magnetized double layers are studied in the local WKB approximation. The corresponding dielectric function shows resonant interaction between fluctuations and electrons whose time of flight across the double layer is an integer multiple of the half period of waves.  相似文献   

19.
We investigate the possibility of localizing various matter fields on the double walls. For spin 0 scalar field, massless zero mode can be normalized on the double walls. However, for spin 1 vector field, the zero mode is not localized on the double walls. In the paper [C.A.S. Almeida, M.M. Ferreira Jr., A.R. Gomes, R. Casana, arXiv:0901.3543 [hep-th]], the authors investigated fermion localization on a Bloch brane, especially, they found fermion resonances on the Bloch brane for both chiralities and related their appearance to branes with internal structure. Inspired by their work, for spin 1/2 spinor field, we focus our attention mainly on the fermion resonances, and also found fermion resonances for both left-handed fermions and right-handed ones on the double walls, which further supports the arguments presented in the paper [C.A.S. Almeida, M.M. Ferreira Jr., A.R. Gomes, R. Casana, arXiv:0901.3543 [hep-th]].  相似文献   

20.
A theoretical scheme for enhanced Kerr nonlinearity is proposed in a four-level ladder-type atomic system based on double dark resonances (DDRs). We solve the relevant density matrix equations in steady state and utilize the perturbation theory to obtain the analytical expressions for the third order susceptibility of the atomic system. The influence of system parameters on behavior of the first and third order susceptibilities is then discussed. In particular, it is found that an enhanced Kerr nonlinearity with reduced linear and nonlinear absorption is obtained around zero probe detuning under the slow light condition through proper adjusting the laser field intensity and frequency detuning of driving fields. The dressed state analysis is employed to explain the physical origin of the obtained result. The obtained results may be important for all-optical signal processing and quantum information technology.  相似文献   

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