Coherent excitons at different orientation arrangements of local transition dipole moments in circular light-harvesting complexes

The coherent exciton plays an important role in the photosynthetic primary process, and its functions are deeply dependent on the orientation arrangements of local transition dipole moments (TDMs). We theoretically and systematically study the physical property of the coherent exciton at different orientation arrangements of the local TDMs in circular light-harvesting (LH) complexes. Especially, if the orientation arrangements are different, the delocalized TDMs of the coherent excitons and the energy locations of the optically active coherent excitons (OACEs) can be obviously different, and then there are more manners to capture, store and transfer light energy in and between LH complexes. Similarly, if the orientation arrangements are altered, light absorption and radiative intensities can be converted fully between the OACEs in the upper and lower coherent exciton bands, and then the blue and red shifts of the absorption and radiative bands of the pigment molecules can occur simultaneously at some orientation arrangements. If the systems are in the vicinities of the critical orientation arrangements, the weak static disorder or small thermal excitation can destroy the coherent electronic excitations, and then the coherent exciton cannot exist any more.     

Hyperfine splitting and isotope shift in the optical transition of Eu isotopes and electromagnetic moments of Eu

The laser-induced resonance fluorescence in an atomic beam was used in order to measure the hyperfine splitting of the 4f ⁷ 6s ² and 4f^{7 6s6p} levels in ^151,153,155Eu isotopes. The hfs constants A and B of the unstable ¹⁵⁵Eu were determined for the first time: MHz, MHz and MHz. With these data and after corrections for second-order hyperfine structure perturbations the nuclear moments of ¹⁵⁵Eu were deduced: n.m. and b. In addition new and more precise values of the hfs constants of the excited state for the stable ^151,153Eu were obtained. They are as follows: MHz, MHz and MHz, MHz. The hyperfine anomalies % and % were extracted from the corrected hfs constants. Received 28 July 1999 and Received in final form 14 January 2000     

Radiative lifetimes and transition moments in MgO

An experimental and theoretical study of several transitions in the MgO molecule is reported. The radiative lifetime of the MgO B¹Σ⁺v'=0 level is measured to be 32.7±1.7 nsec, while that of the electronic state(s) excited by 372 nm radiation (d³Δ and/or f³Π) is 11.8±0.5 nsec. The B-X and A-X transition moments are calculated using state averaged multiconfiguration self-consistent field and configuration interaction methods. With an estimate of the B-A transition moment derived from an earlier calculation, the radiative lifetime of the B¹Σ⁺v'=0 level is computed to be 24 nsec. A value of 0.23 msec is calculated for the lifetime of A¹Πv'=0.     

Baryon multipole moments in the single quark transition model

It is shown that the predictions of the single quark transition model of the electromagnetic transitions of baryons can be expressed in a highly simplified form by the simultaneous use of multipole moments at the quark level and at the baryon level. The predictions so expressed are applied to the latest ‘world average’ photoproduction amplitudes and an excellent fit is obtained. The model also fits electroproduction amplitudes to within the errors. It is argued that the electromagnetic decays of baryon resonances to dileptons are of particular interest and widths for these processes are estimated.     

Pattern recognition by optical moments

A new method is described for pattern recognition employing moments derived from the diffraction pattern of the object     

Local moments and magnetic ordering in transition metals

Stoner theory predicts a complete collapse of the local magnetic moment at the Curie temperature. In this paper, the effect of local moment formation in the non-magnetic state is discussed. The energy between the magnetic and non-magnetic state is found to be considerably reduced. This observation is consistent with the low observed magnetic ordering temperatures of the 3d metals when compared to the values derived from band theory.     

Iodine magnetic moments measured by on-line nuclear orientation

On-Line measurements of magnetic dipole moments of^117–122I are interpreted using coupling of the odd particles to a deformed core. The results show interesting effects of g_7/2, d_5/2 orbital admixtures in the odd-A isotopes, which are close to spherical. The odd-odd isotopes^{118, 120}I show clear examples of shape co-existence.     

A method of moments for the optical Jahn-Teller problem

A Method of moments is presented for optical transitions to Jahn-Teller states. The Condon and a modified Born-Oppenheimer approximation have been adopted. On the basis of these 2 principles, the method is exact. Specific orthonormality and closure properties are derived for Jahn-Teller states, which are essential for performing the calculation. As illustrative examples the pure Jahn-Teller casesE-e andT-t have been calculated in the strong coupling limit. Each of these cases leads to specific combinatorial problems and to an application of Wick's theorem. The latter is common to both cases. Comparison with the semi-classical calculation reveals the identity of the results for theE- e system.     

大气湍流中光束的高阶强度矩

研究了光束通过大气湍流传输的高阶强度矩, 提出了大气湍流中光束高阶强度矩的推导方法, 并推导出了一至四阶光束强度矩传输的解析表达式. 所得结果具有一般性,任意某一光束在自由空间和大气湍流中传输的高阶强度矩均可作为本文结果的特例. 另一方面, 以高斯光束为例, 研究了其K参数在湍流大气中的传输规律. 研究表明,高斯光束在大气湍流中其K参数并不是一个传输不变量,它与传输距离、束腰半径、湍流内外尺度以及湍流强度均有关.这个结论与采用Rytov相位结构函数二次近似或强湍流近似下的结论不同,本文给出了合理解释. 关键词： 高阶强度矩 大气传输 大气湍流 K参数')" href="#">K参数     

Electromagnetic transition strengths and nuclear moments in123Xe

The level structure of¹²³Xe has been studied with the¹¹⁴Cd (¹²C, 3n) and^?Cd (¹³C, 4n) reactions using in-beamγ-ray spectroscopy. The yrast cascade on the low lying odd parity states originating from theh _11/2 neutron orbital has been investigated yielding lifetimesτ of 18(3) ps, 2.2 (4) ns and 17(2) ns for the 15/2^?, 11/2^? and 9/2^? states, respectively. Theg-factor of thet _1/2=5.2 μs isomer has been measured to beg=?0.256(2). From the time differential observation of the electric quadrupole interaction in a¹¹⁴Cd single crystal the spin of this isomer has been determined to be 7/2 and from the coupling constante ² Qq/h=116(2) MHz the quadrupole moment was deduced. The results are discussed in the framework of the triaxial rotor plus particle model.     

Spectral moments and orientation correlation functions of asymmetric top molecules

A method for calculating the spectral moments of dipole absorption and Raman scattering by asymmetric top molecules is proposed. The method is based on the calculation of coefficients of expansion of the corresponding orientation correlation functions in a Taylor series using the formalism of the angular momentum theory.     

Measurements of the electronic transition moments of C2-band systems

Electronic transition moments of seven C₂ singlet and triplet band systems, which are in the 0·2?1·2μm spectral region, have been measured. The measurements were made in emission behind incident shock waves in C₂H₂-argon mixtures. Narrow band-pass radiometers were used to obtain absolute measurements of shock-excited C₂ radiation from which absolute electronic transition moments are derived by a synthetic spectrum analysis. New results are reported for the Ballik-Ramsay, Phillips, Swan, Deslandres-d'Azambuja, Fox-Herzberg, Mulliken, and Freymark Systems.     

A theoretical study of the effect of disorder of the transition dipole moments of molecules on the shape of optical bands of molecular aggregates

Aggregates with substitutional disorder, in which molecules of different types have different transition dipole moments, are considered. The relations between the absorption spectra of aggregates with disordered and nondisordered transition dipole moments are obtained for two limiting cases: (1) the case when there is no statistical correlation between the transition energies and transition dipole moments of the molecules and (2) the case of total correlation, when the transition energies and transition dipole moments are strictly related to each other. For aggregates that are characterized by substitutional disorder along with diagonal disorder, an effective method of calculation of the optical bands is developed. Numerical calculations of the absorption bands of aggregates consisting of molecules of two types are carried out at different values of the parameters.     

Systematics of diatomic molecular transition moments: Encouraging progress

Literature absolute transition moments for A-X (0-0) bands have been used to obtain “best” values of R_e for some 30 molecules. For isoelectronic sequences, R_e vs Z (heavy)/Z (light) is steeper at abscissae near 1.0 than a larger abscissae, contrary to expectation. For isovalent sequences, e.g. CH, SiH, R_e (WY) is in each lower (average, 53%) than R_e (WX). Suggestions will emerge for measurements which would be helpful in furthering diatomic molecular transition moment systematics.     

Determination of transition dipole moments from time-resolved photoelectron spectroscopy

We show how to extract the energy- and coordinate dependence of dipole-moments for a neutral-to-ionic molecular transition from time-resolved photoelectron spectra. The procedure needs the potential surfaces of the neutral and the cationic state which are involved in the ionization process as an input. Given these potentials and the laser parameters it is possible to determine the functional form of the transition dipole moment from the measured time- and energy-resolved transient signals.Received: 28 February 2003, Published online: 29 April 2003PACS: 31.70.Hq Time-dependent phenomena: excitation and relaxation processes, and reaction rates - 33.80.Wz Other multiphoton processes     

Light-induced orientation transition in nematic liquid crystalline polymer

Optical orientation in transparent nematic liquid crystalline polymer (NLCP) was observed for the first time. In NLCP with dye dopant, the light-induced second-order orientation transition being an analogue of the Freedericksz transition in low-frequency fields is found. The transition threshold is ~10 μW which is lower than the threshold of the light-induced Freedericksz transition in low-molecular nematics by four orders ofmagnitude and is lower than the characteristic value for low-molecular nematics with dye dopant by two orders of magnitude.     

Effect of the ratio of transition dipole moments on few-cycle pulse propagation

Propagation of a few-cycle laser pulses in a dense V-type three-level atomic medium is investigated based on full-wave Maxwell-Bloch equations by taking the near dipole-dipole (NDD) interaction into account. We find that the ratio, γ, of the transition dipole moments has strong influence on the time evolution and split of the pulse: when γ≤ 1, the NDD interaction delays propagation and split of the pulse, and this phenomenon is more obvious when the value of γ is smaller; when γ = 2, the NDD interaction accelerates propagation and split of the pulse.     

Electromagnetic moments and transition rates from cranking model wavefunctions

Simplified formulas are derived for the angular-momentum projected matrix elements of the electromagnetic transition probabilities and spectroscopic moments using microscopic cranking model wavefunctions. They are compared with exact calculations.