Stark deceleration of CaF molecules in strong- and weak-field seeking states

We report the Stark deceleration of CaF molecules in the strong-field seeking ground state and in a weak-field seeking component of a rotationally-excited state. We use two types of decelerator, a conventional Stark decelerator for the weak-field seekers and an alternating gradient decelerator for the strong-field seekers, and we compare their relative merits. We also consider the application of laser cooling to increase the phase-space density of decelerated molecules.     

A linear AC trap for polar molecules in their ground state

A linear AC trap for polar molecules in high-field seeking states has been devised and implemented, and its characteristics have been investigated both experimentally and theoretically. The trap is loaded with slow 15ND3 molecules in their ground state (para-ammonia) from a Stark decelerator. The trap's geometry offers optimal access as well as improved loading. We present measurements of the dependence of the trap's performance on the switching frequency, which exhibit a characteristic structure due to nonlinear resonance effects. The molecules are found to oscillate in the trap under the influence of the trapping forces, which were analyzed using 3D numerical simulations. On the basis of expansion measurements, molecules with a velocity and a position spread of 2.1 m/s and 0.4 mm, respectively, are still accepted by the trap. This corresponds to a temperature of 2.0 mK. From numerical simulations, we find the phase-space volume that can be confined by the trap (the acceptance) to be 50 mm3 (m/s)3.     

Deceleration of supersonic beams using inhomogeneous electric and magnetic fields

Methods for the production of cold atomic and molecular samples relying on the deceleration of pulsed supersonic beams are described and a review of the corresponding literature is presented. These methods include multistage Stark deceleration, multistage Zeeman deceleration, and Rydberg-Stark deceleration. Recent applications of the cold samples produced with these techniques are summarized.     

He(23S1)、Ne(3P0,2)与NH3的传能动力学

在分子束条件下利用化学发光技术研究了亚稳态惰性气体原子He（23S1）和Ne（3P0，2）与NH3碰撞的解离激发反应．He（23S1）与NH3的反应中观察到NH（A－X，c－a，c－b），NH＋（B－X）和H*－Balmer发射．对NH（A－X，c－a）的谱图进行了拟合．分析NH（c－b）谱发现NH（c）倾向于生成具有f对称性的转动能级，NH3可能是经由一个NH2中间体分两步解离，这与121．6nm光解NH3时的倾向性正好相反．利用参比反应测得生成NH（A，c）的速度为k＝1．0×10－11cm3•s－1．He（23S1）与NH3生成的NH（A，v’＝1）的转动激发比v’＝0时要高，根据含角动量守恒的相空间理论，其生成过程可能具有较大的解离半碰撞参数．Ne（3P0，2）与NH3反应只有NH（A－X，c－a）发射，NH（A，c）的振转布居可由简单相空间理论三体解离模式解释．     

Stopping paramagnetic supersonic beams: the advantage of a co-moving magnetic trap decelerator

The long standing goal of chemical physics is finding a convenient method to create slow and cold beams intense enough to observe chemical reactions in the temperature range of a few Kelvin. We present an extensive numerical analysis of our moving magnetic trap decelerator showing that a 3D confinement throughout the deceleration process enables deceleration of almost all paramagnetic particles within the original supersonic expansion to stopping velocities. We show that the phase space region containing the decelerating species is larger by two orders of magnitude as compared to other available deceleration methods.     

Velocity map imaging of a slow beam of ammonia molecules inside a quadrupole guide

Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole, while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with horizontal and vertical slits is used. A velocity resolution of 35 m s(-1) is obtained. It is shown that signal due to thermal background can be eliminated, resulting in the detection of slow molecules with an increased signal-to-noise ratio. As an illustration of the resolving power we have used the velocity map imaging system to characterize the phase-space distribution of a Stark decelerated ammonia beam.     

Resonances in rotationally inelastic scattering of OH(X2Π) with helium and neon

We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH (X(2)Π, j = 3/2, F(1), f) radicals with He and Ne atoms. We calculate new ab initio potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare well with the recent crossed beam scattering experiment of Kirste et al. [Phys. Rev. A 82, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.     

A dinuclear MnIII-CuII single-molecule magnet

The reaction of 1/3 equivalent of CuCl2.2H2O with MnCl2.4H2O and 5-bromo-2-salicylideneamino-1-propanol (H(2)5-Br-sap) in methanol gave dark brown crystals of [MnIIICuIICl(5-Br-sap)2(MeOH)] (1). Complex 1 has an alkoxo-bridged dinuclear core of MnIII and CuII ions, which have elongated octahedral and square-planar coordination geometries, respectively. In dc magnetic susceptibility measurements, chi(m)T values increased as the temperature was lowered, followed by a sudden decrease below 20 K. This behavior is indicative of the occurrence of intramolecular ferromagnetic interactions, and fitting gave an S=5/2 spin ground state with an exchange coupling constant J(MnCu) of +78 cm(-1). Magnetization data collected as a function of temperature and applied magnetic field were analyzed by using a spin Hamiltonian with isotropic Zeeman and axial zero-field splitting (ZFS) terms, and a negative D(5/2) value (-1.86 cm(-1)) was obtained. A high-field EPR (HFEPR) spectrum (342.0 GHz) at 4.2 K was composed of four peaks, and two additional peaks at higher magnetic field appeared as the temperature was increased. The temperature dependences in the HFEPR spectra are indicative of a negative D(5/2) value, and fitting of the data gave D(5/2)=-1.81 cm(-1). In the ac magnetic susceptibility measurements, frequency dependent in-phase (chi(m)') and out-of-phase (chi(m)') signals with peak maxima at 0.7-1.5 K were observed and small peaks below 0.7 K appeared. The ac susceptibility data supports that 1 is a single-molecule magnet (SMM). Arrhenius plots for the chi(m)' peaks from 0.7-1.5 K gave the re-orientation energy barrier (DeltaE) of 10.5 K with a pre-exponential factor of 8.2x10(-8) s.     

Coherent control of collision processes: Penning versus associative ionization

Coherent control theory is applied to the control of Ne*(3s,(3)P2)+Ar((1)S0) collisions and computations are shown that display extensive control over these processes. Indeed we demonstrate that it is possible to essentially turn on and off the cross sections for both the Penning and associative ionization processes. This facility arises from the interference between matter waves induced by creating a linear superposition of the degenerate M={-2,-1,0,1,2} Zeeman sublevels of the Ne*(3s,(3)P2) target atom. The computations, conducted at collision energies in the 1-8 kcal/mole range, are based on combining, within the "rotating atom approximation," empirically derived and ab initio ionization widths.     

Construction and performance of an a.c. modulated magnet for Zeeman atomic absorption spectroscopy

A Zeeman atomic absorption spectroscopy system has been constructed utilizing a 50 Hz sine wave modulated magnetic field that can be directed either parallel or perpendicular to the optical axis. The amplitude of the magnetic field strength is adjustable up to 10 kG at a maximum power consumption of 0.7 kW.The readout system allows normal atomic absorption as well as d.c. and a.c. Zeeman atomic absorption measurements. Plots of experimental sensitivity vs magnetic field strength and analytical curves are in agreement with theoretical predictions.Experiments in the presence of filter simulated and real background absorbance show that the described Zeeman instrument is capable of correcting background absorption up to two absorbance units.     

Application of the zeeman effect to analytical atomic spectroscopy-III Extension of calibration curves

An application of the Zeeman effect is described by which calibration curves applicable to high analyte concentrations may be obtained. The procedure uses single-beam measurements on the displaced σ-components of the Zeeman multiplet, and thus permits controlled desensitization of an atomic-absorption signal to be obtained, simply by increasing the magnetic field strength, while leaving the monochromator permanently set on the optimum analytical line for the element considered. Calibration curves for Ca, Cd and Cu are given for applied field strengths from 0 to 16kG.     

Zeeman effect in CaF(2Pi(3/2))

The Zeeman effect in the excited A 2Pi(3/2) state of CaF is measured and analyzed over a wide range of magnetic fields. It is found that the splitting of the Zeeman levels is largely determined by the coupling between different rotational states and there are no low-field seeking states in the J=3/2 manifold of Zeeman levels at high magnetic fields. A model of the Zeeman spectrum based on the ligand-field theory of CaF is shown to be accurate in the interval of magnetic fields 0-5 Tesla. This demonstrates that the magnetic moment of the CaF(A 2Pi(3/2)) molecule is effectively determined by the spin angular momentum of a single electron and the orbital motion of the valence electron around the Ca2+ core. An analysis of the Zeeman spectrum as a function of the molecular rotational constant indicates that 2Pi(3/2) molecules should have significant rotational constants (at least as large as twice the rotational constant of CaF) to be amenable to magnetic trapping in high fields.     

Influence of Jahn-Teller coupling on the magnetic properties of transition metal complexes with orbital triplet ground terms: magnetization and electronic Raman studies of the titanium(III) hexa-aqua cation

Magnetization and electronic Raman data are presented for salts of the type Cs[Ga:Ti](SO(4))(2) x 12H(2)O, which enable a very precise definition of the electronic structure of the [Ti(OH(2))(6)](3+) cation. The magnetization data exhibit a spectacular deviation from Brillouin behavior, with the magnetic moment highly dependent on the strength of the applied field at a given ratio of B/T. This arises from unprecedented higher-order contributions to the magnetization, and these measurements afford the determination of the ground-state Zeeman coefficients to third-order. The anomalous magnetic behavior is a manifestation of Jahn-Teller coupling, giving rise to low-lying vibronic states, which mix into the ground state through the magnetic field. Electronic Raman measurements of the 1%-titanium(III)-doped sample identify the first vibronic excitation at approximately 18 cm(-1), which betokens a substantial quenching of spin-orbit coupling by the vibronic interaction. The ground-state Zeeman coefficients are strongly dependent on the concentration of titanium(III) in the crystals, and this can be modeled as a function of one parameter, representing the degree of strain induced by the cooperative Jahn-Teller effect. This study clearly demonstrates the importance that the Jahn-Teller effect can have in governing the magnetic properties of transition metal complexes with orbital triplet ground terms.     

Reactive scattering of a neon seeded oxygen atom beam

A high pressure microwave discharge source operating with a dilute mixture of O₂ in Ne has been used to produce a supersonic nozzle beam of O atoms seeded in Ne. This low energy supersonic O atom beam has been used to study the reactive scattering of O atoms with Cl₂ and CS₂ molecules at an initial translational energy E = 13 kJ mol^?1. The results are compared with rective scattering from the same reactions using a high energy O atom beam formed by seeding O atoms in He. The O + Cl₂ reaction proceeds via a short-lived collision complex where the lifetime of the collision complex depends upon the initial translational energy. However the O + CS₂ reaction follows a stripping mechanism which is unaffected by initial translational energy.     

Gas-phase 21Ne NMR studies and the nuclear magnetic dipole moment of neon-21

Gas-phase ²¹Ne nuclear magnetic resonance spectra were measured at the natural abundance of ²¹Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B₀ = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the ²¹Ne nuclear magnetic moment, μ(²¹Ne) = 0.6617774(10) μ_N. The present value of μ(²¹Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(²¹Ne).     

Superfluorescent transitions in an external magnetic field

Polarisation properties of the superfluorescence in the near-infrared regime have been investigated between high-lying levels of Sr and Ba under the influence of a static homogeneous external magnetic field. In some transitions the time-resolved measurements show a change of the polarisation of the superfluorescence depending on the magnetic field strength. In suitable experimental conditions intensity modulations were observed. These were assigned as Zeeman quantum beats or indirectly observed Zeeman superfluorescent beats. The experimental findings of superfluorescence in two-level, three-level, or multi-level configurations in dependence on the magnetic field strength can be explained well in a semiclassical model of multi-level superfluorescence.     

Electron spin resonance g tensors for complexes of Ne and Ar with AlO: theoretical studies related to the large matrix effect observed for AlO

For Ne(n)-AlO (n=2, 4, 6, 8, 10) and Ar(n)-AlO clusters (n=2, 4, 6, 8), the perpendicular (relative to AlO) component of the g tensor was calculated by second-order perturbation theory, using multireference configuration-interaction wave functions. The rare-gas (Rg) atoms were placed axially and/or off axially (one or two rings of four Rg atoms each), and the distance of the Rg atoms from the Al and O atoms, or from the AlO axis, was varied from 4 to 12 bohrs. Rg atoms placed axially mostly increase g(perpendicular), whereas off-axially placed ones lower it below the gas-phase value of AlO. The largest deviations from g(perpendicular) of isolated AlO occur at Ne-Al,O distances of 5-6 bohrs, and Ar-Al,O distances of 6-9 bohrs, with maximal lowerings of about 1600 ppm for Ne and about 2200 ppm (estimated) for Ar in the case of two axial and eight off-axial Rg atoms. Electron spin resonance studies by Knight and Weltner found large matrix effects for AlO, with downshifts of g(perpendicular) observed to be about 450 and 1150 ppm in Ne and Ar matrices, respectively.     

An inertial model of atoms: atomic spectra as a resonance problem

A new model of atoms based on the theory of material waves is proposed. Atoms are characterized by an inertial aggregation of negative charge within the atomic shell, the calculation yields, for hydrogen atoms, an atomic radius of 0.470 nm. Atomic spectra result from radial material waves, quantization being the consequence of boundary conditions imposed on the fundamental wave equation. Stark effects and Zeeman effects are treated in detail, they are referred to deformations and rotations of the atomic shell. An analysis of Stern--Gerlach experiments bases subsequent deflections of single atoms on rotations and interactions of magnetic fields.     

具有十二元环空旷骨架的Mn3Al6(PO4)12·4tren·11H2O的水热合成与表征

自从1982年美国联合碳化公司(U.C.C.)开发出系列磷酸铝分子筛(AlPO4-n,n代表不同的骨架类型)[1]以来,新型微孔结构磷酸铝的开发一直吸引着人们的广泛关注[2].与此同时,杂原子磷酸铝分子筛的研究受到了人们的高度重视,许多元素(Fe,Mn,Co,Zn等)可以作为杂原子进入磷酸铝的分子筛骨架[3～5].其中,含有特殊催化活性的过渡金属离子Mn的磷酸铝备受关注[6,7].1999年,徐耀华等[8]合成出具有新颖三维开放骨架的磷酸铝Al9(PO4)12(C24H91N16)·17H2O.最近,Beitone等[9,10]研究了Zn和Fe元素在此骨架中的取代情况.本文中,我们首次将Mn元素引入…