Theoretical analysis of the coupling between Feshbach states and hyperfine excited states in the creation of ~(23)Na~(40)K molecule

We present an intensive study of the coupling between different Feshbach states and the hyperfine levels of the excited states in the adiabatic creation of ~(23)Na~(40)K ground-state molecules.We use coupled-channel method to calculate the wave function of the Feshbach molecules,and give the short-range wave function of triplet component.The energies of the hyperfine excited states and the coupling strength between the Feshbach states and the hyperfine excited states are calculated.Our results can be used to prepare a specific hyperfine level of the rovibrational ground state to study the ultracold collisions involving molecules.     

基于电子顺磁共振的ZnTPP激发态及其TEMPO各向异性的研究

为了研究卟啉类敏化剂的光致激发态能量转移和电子转移问题,本文基于紫外可见光谱仪和电子顺磁共振波谱仪,构建了以锌卟啉为研究对象的"锌卟啉-稳态自由基-二甲苯"实验体系.锌卟啉的紫外可见光谱显示,在可见光谱的B带和Q带出现明显的特征峰,是锌卟啉分子中电子由基态能级跃迁至激发态能级产生的.低温条件下受紫外可见光辐照的实验体系的电子顺磁共振波谱,检测到了稳态自由基四甲基哌啶氧化物的增强吸收电子顺磁共振波谱.根据分子激发态相关理论、光化学物理反应理论和化学诱导电子自旋极化理论对实验结果进行了分析,结果表明,四甲基哌啶氧化物稳态自由基电子顺磁共振波谱的增强吸收对应于锌卟啉光致激发态的能量转移和电子转移;四甲基哌啶氧化物在低温(143 K)下的电子顺磁共振波谱表现出的各向异性特征现象来源于氮氧自由基电子与氮核的各向异性超精细相互作用.     

Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of 25Mg+

We have employed the relativistic coupled cluster theory to calculate the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of singly ionized magnesium. Comparison with experimental and the other theoretical results are done and predictions are also made for a few low lying excited states which could be of interest. We have made comparative studies of the important many body effects contributing to the hyperfine constants for the different states of the ion.     

Speed of sound in an optical lattice

A system of equal mixture of ⁶Li atomic Fermi gas of two hyperfine states loaded into a cubic three‐dimensional optical lattice is studied assuming a negative scattering length (BCS side of the Feshbach resonance). When the interaction is attractive, fermionic atoms can pair and form a superfluid. The dispersion of the phonon‐like mode and the speed of sound in the long‐wavelength limit are obtained by solving the Bethe‐Salpeter equations for the collective modes of the attractive Hubbard Hamiltonian.     

Giant resonances on excited states

We derive modified RPA equations for small vibrations about excited states. The temperature dependence of collective excitations is examined. The formalism is applied to the ground state and the first excited state of ⁹⁰Zr in order to confirm a hypothesis which states that not only the ground state but every excited state of a nucleus has a giant resonance built upon it.     

探测功率展宽效应引起的电磁诱导透明向电磁诱导吸收的转化

本文对准型四能级系统中探测功率展宽效应引起的非线性效应进行了理论研究。准型四能级系统包括三个基态精细结构能级和一个激发态能级,除光学耦合场和探测场分别激励一个基态精细结构能级和激发态能级之间的跃迁外,附加了一个射频驱动场作用于其中一个基态精细结构能级和另一个新的基态精细结构能级之间,并通过与耦合场驱动共同能级建立量子相关性。研究结果表明,在射频驱动场的辅助激励下,探测功率展宽效应不仅可以使EIT的线宽增宽,还能引起吸收曲线中的类色散特性,使EIT最终变化为EIA。     

Nuclear reactions as an example of the quantum theory of irreversible processes

A modification of the atomic beam magnetic resonance method for investigation of the hyperfine structure of excited atomic states will be described. Radiofrequency transitions between the hyperfine structure niveaus of the excited state, which are unequally populated by circularly polarized light, are detected by observing the resulting change in population number of the hyperfine structure niveaus of the ground state using magnetic deflection in an inhomogeneous field and additional radiofrequency transitions in the ground state as analyzers. As an application the hyperfine structure of the excited 4² P _3/2-state of K³⁹ has been investigated in an almost strong magnetic field of about 65 G with a constant frequency of the applied radiofrequency field of 125.50 Mc/s. The analysis of the radiofrequency signal of the excited state detected as a change in the amplitude of a radiofrequency transition in the ground state yielded the valuesA=(6.10±0.25) Mc/s andB=(1.8±1.2) Mc/s for the hyperfine structure constants of the 4² P _3/2-state of K³⁹. Further possibilities for observing signals of the excited state with the apparatus used in this experiment are also discussed.     

Hyperfine-structure studies of the 1s<Superscript>2</Superscript>2snp (n=2, 3) <Superscript>3</Superscript>P states for the beryllium isoelectronic sequence

The hyperfine structure parameters of the 1s²2snp (n=2, 3) ³P states for the beryllium isoelectronic sequence from Z= 4 to 10 are calculated with the full-core plus correlation (FCPC) wave functions. For the 1s²2s2p ³P state of the beryllium atom, the calculated fine structure parameters are in good agreement with the latest theoretical and experimental data in the literature. It is shown that hyperfine constants of the low-lying excited states for the beryllium atom can be calculated accurately using this theoretical method. For 1s²2snp (n=2, 3) ³P states of the beryllium isoelectronic sequence, our predictions may provide valuable reference data for other theoretical calculations and experimental measurements in future.     

Optical pumping and coherence effects in fluorescence from a four level system

An effective four-level system around the D2 line of ⁸⁵Rb at room temperature, is experimentally investigated by fluorescent studies under the action of two driving fields L1 and L2. This system exhibits unique features in fluorescence as a function of frequency separation between L1 and L2. In particular, at two-photon resonance, when the Rabi frequency of L1 exceeds that of L2, signatures of Electromagnetically Induced Transperancy effect (EIT) arising from the three-level Λ sub-system is present as a sub-natural dip in fluorescence from the fourth level. At comparable strengths of L1 and L2 the fluorescence features indicate a regime, where the effects arising from optical pumping and EIT effect due to ground hyperfine level coherence coexist. We see in the coexistence regime, saturation effects arising from difference frequency crossing (DFC) resonances and optical pumping around the EIT window. At low strengths of L1, all signs of coherence vanishes from the system and the fluorescent features result from incoherent optical pumping through the Autler-Townes split states of the excited state hyperfine levels, which are split due to the stronger L2 laser. The dominant role of the L1 laser in creating a robust transparency signal even in the presence of an off-resonant excitation is brought out. The results are supported by density matrix calculations.     

An investigation of the structure of free-base porphycene by time-resolved electron nuclear double resonance and density functional theory on the photoexcited triplet state

The photoexcited triplet state of free-base porphycene has been investigated by time-resolved electron nuclear double resonance spectroscopy at 10 K. In order to determine whether porphycene is cis or trans configured, experimentally determined A_zz hyperfine coupling tensor components are compared with those predicted from density functional theory. The structures of cis and trans porphycene, in both the singlet ground state and lowest excited triplet state were calculated using the Becke3-Lee-Yang-Parr composite exchange correlation functional and the 6–31G* basis set. Hyperfine couplings for these structures were then calculated using the same functional but with the extended EPR-II basis set. From the results it can be concluded that porphycene has a trans configuration in both the ground singlet and lowest excited triplet state. Additionally, the significant differences in structure between the singlet and triplet states are reflected in the calculated hyperfine couplings, with those for the trans conformation in the triplet state in reasonable agreement with the experimental values.     

Influence of the hyperfine structure of the atomic states on the collective effects in the Rb<Subscript>2</Subscript> quasi-molecule

A consistent quantum approach is used to study the influence of intraatomic spin–orbit and hyperfine interactions on the character of a resonance dipole–dipole interatomic interaction and, hence, collective effects. For this purpose, the collective spontaneous decay of excited states and the spectral dependence of the total scattering cross section of a monochromatic light wave are analyzed in the system consisting of two rubidium-87 atoms. The modification of the radiation properties and the interaction of the atoms with external radiation are studied as functions of the interatomic distance. The presence of a complex structure of the sublevels of both the ground and excited states is shown to modify the collective effects substantially as compared to the case when this structure is absent.     

Two-color coherent population trapping in a single Cs hyperfine transition,with application in magnetometry

We investigate the coherent population trapping effect occurring between the Zeeman sublevels of a given hyperfine state of Cs when excited by a single-mode diode laser, which is frequency modulated in the kHz–MHz range. In the presence of a dc magnetic field, simultaneous excitation of pairs of ground-state magnetic sublevels to common excited magnetic sublevels is performed. As a result, coherent population trapping resonance is detected at only a given modulation frequency, whose value gives a measure of the magnetic field. The parameters of the resonances are measured in order to determine the ultimate accuracy of the magnetic field measurement. Received: 6 December 2002 / Revised version: 24 February 2003 / Published online: 2 June 2003 RID="*" ID="*"Corresponding author. Fax: +39-0577/23-4689, E-mail: biancalana@unisi.it     

On the possibility of electric transport mediated by long living intrinsic localized solectron modes

We consider a polaron Hamiltonian in which not only the lattice and the electron-lattice interactions, but also the electron hopping term is affected by anharmonicity. We find that the one-electron ground states of this system are localized in a wide range of the parameter space. Furthermore, low energy excited states, generated either by additional momenta in the lattice sites or by appropriate initial electron conditions, lead to states constituted by a localized electron density and an associated lattice distortion, which move together through the system, at subsonic or supersonic velocities. Thus we investigate here the localized states above the ground state which correspond to moving electrons. We show that besides the stationary localized electron states (proper polaron states) there exist moving localized solectron states which can be easily excited. The evolution of these localized states suggests their potential as new carriers for fast electric charge transport.     

ESR studies of Cu2+ doped in triglycine calcium bromide single crystals

Electron spin resonance studies were carried out on Cu²⁺ doped triglycine calcium bromide. The spectra recorded at room temperature revealed well-resolved hyperfine spectra of⁶³Cu superposed with super-hyperfine lines due to¹⁴N nuclei. The spin Hamiltonian parameters are evaluated. It was concluded that the Cu²⁺ enters the lattice interstitially.     

Sub-collision hyperfine structure of nonlinear-optical resonance with field scanning

Some experimental evidences for methane are produced that the simple transition from frequency scanning of nonlinear-optical resonances to magnetic one may be accompanied with transition from sub-Doppler collisionally broadened structure to sub-collision hyperfine one. It is conditioned by nonlinearity of splitting of hyperfine sublevel for molecules in the adiabatically varied magnetic field and, respectively, breaking the analogy of magnetic and frequency scannings. The exact calculation of the resonance structure is considered for molecules with only one spin subsystem. The approximately spin-additive calculation of the structure is given for sufficiently fast rotating molecules with greater number of spin subsystems. Within the same approximation an example of hyperfine doubling in the magnetic and electric spectra of nonlinear-optical resonance is considered for fluoromethane.     

Bound states and resonance states of the plasma-embedded tdμ and ddμ molecular ions

We have investigated the bound states and resonance states of plasma-embedded tdμ and ddμ molecular ions using accurate correlated basis functions. The plasma effect has been taken care of by considering the Debye shielding approach of plasma modeling which admits a variety of plasma conditions. The density of resonance states are calculated using the stabilization method. The ground and excited states energies, and the S-wave resonance energies of tdμ and ddμ molecular ions immersed in plasmas are reported for various shielding parameters, along with the 1S and 2S threshold energies of the tμ and dμ atoms.     

Hyperfine fields amd electronic structure of non-magnetic impurities in iron

Hyperfine fields of non-magnetic impurities in iron are calculated using the local-density formalism in an embedded cluster model. The hyperfine fields are seen to result from a delicate balance between negative exchange polarized “bound-paired” states and positive “unpaired-band” contributions. Pressure and temperature dependence and effects due to lattice relaxation are discussed.     

Relativistic coupled cluster method

Relativistic coupled cluster method (CCM) is applied to compute the low lying excited and ion states of strontium and ytterbium atom. The resulting excitation and ionization energies are in excellent agreement with experimental data and with other correlated calculations. The nuclear magnetic dipole hyperfine constants (A) and electric quadrupole hyperfine constants (B) of excited states are also evaluated and are in accord with experiment. We further address the basis set dependency of the computed properties.     

Directional behavior of nuclear quadrupole resonance in YBa2Cu3O6

Powder samples of YBa₂Cu₃O₆ were magnetically aligned and the anisotropies in the systems were studied by means of Cu(1) nuclear quadrupole resonance (NQR) in the absence of external magnetic fields. Our room temperature measurements of the NQR lineshapes and the spin–lattice and spin–spin relaxation times as a function of the aligning magnetic field indicate that full microscopic alignment can be achieved by using a magnetic field of about 4.7 T, for which doublet line patterns arising from a hyperfine splitting were observed.     

Isotope shifts and hyperfine structure in the transitions of gadolinium

High-resolution resonance ionization mass spectrometry has been used to measure isotope shifts and hyperfine structure in all (J = 2-6) and the transitions of gadolinium (Gd I). Gadolinium atoms in an atomic beam were excited with a tunable single-frequency laser in the wavelength range of 422-429 nm. Resonant excitation was followed by photoionization with the 363.8 nm line of an argon ion laser and resulting ions were mass separated and detected with a quadrupole mass spectrometer. Isotope shifts for all stable gadolinium isotopes in these transitions have been measured for the first time. Additionally, the hyperfine structure constants of the upper states have been derived for the isotopes ^{155, 157} Gd and are compared with previous work. Using prior experimental values for the mean nuclear charge radii, derived from the combination of muonic atoms and electron scattering data, field shift and specific mass shift coefficients for the investigated transitions have been determined and nuclear charge parameters for the minor isotopes ^{152, 154} Gd have been calculated. Received 18 November 1999