Reaction products from a discharge of N2 and H2S: The microwave spectrum of NH2SH

Thiohydroxylamine has been identified as one of the reaction products from the discharge reaction of N₂ + H₂S. Both cis and trans conformers have been observed. The rotational spectra have been studied from 56 to 170 GHz for the normal species and several deuterated isotopic species of each conformer. The electric dipole moments of both conformers have been determined. A number of the transitions of the cis conformer exhibit splittings due to the nuclear quadrupole moment of the ¹⁴N nucleus. A least squares fit of the frequency splittings have led to an analysis of the eQq values. Ab initio calculations using a 4-31G basis set both with and without polarization functions have been carried out to aid in the analysis and to provide a final structural comparison with the microwave results.     

Parelektrische Resonanz von Li+ in KCl

Parelectric resonance (PER) absorption spectra of Li⁺-centers in KCl crystals are measured at 35 and 9 GHz. Measurements for the microwave fieldE ₁ parallel and perpendicular to the static fieldE ₀ for three different orientations relative to the crystal axes can be explained by using the following offcenter tunneling model for the Li⁺-center: The dipole momentp=6.3±0.3 Debye is in [111] direction. Tunneling transitions are possible parallel to the [100] and [110] axis. The corresponding matrix elements are 11.3±0.5 and 3.2±0.5 GHz. The zero field splittings are 9.8±1.5; 22.6±1 and 35.4±3 GHz. Measurements under application of an uniaxial pressureP ₀ support this analysis.     

Submillimetre EPR spectrometer

A wide-band submillimetre EPR spectrometer is described. A set of tunable backward wave oscillators and quasioptic lens system enables one to operate in the frequency region 79–535 GHz. The sample is placed in a magnetic field of up to 1 T at 4.2 K. The spectrometer is intended for the investigation of EPR spectra of rare-earth ions in solids with zero field splittings of the ground states near the frequency of operation and/or electron systems with ag-factor exceeding 5. The spectrometer’s capabilities are demonstrated with an investigation of the EPR spectra of Dy²⁺ and Dy³⁺ ions in CaF₂. As a result the exact value of the zero field splitting between the ground Γ₈ quartet and the first exited Γ₇ doublet of Dy³⁺ in CaF₂, Δ=257±0.5 GHz, has been measured directly.     

A new paraelectric center in lithium-doped KBr

We report paraelectric resonance measurements for KBr:Li⁺⁷ and KBr:Li⁺⁶. The observed zero-field splittings are large - 62, 65, and 141.5 GHz ± 1 GHz in KBr:Li⁺⁷, and 88 and 118 GHz ± in KBr:Li⁺⁶ — giving an isotope shift of 40% for the lower lines. The uncorrected dipole moment is p = 0.98 ± 0.05 eA. The presence of OH^- seems to suppress the Li⁺ signal.     

Leptonic dipole moments in the left-right supersymmetric model

The observation of neutrino oscillations imposes a pattern of mixing in both the sneutrino and charged slepton sectors. On the other hand, the apparent 2.6 deviation of the anomalous magnetic moment of the muon from the standard model value favors a scenario beyond the standard model. We show that, in a supersymmetric model with left-right symmetry, which provides an explanation for both phenomena, the relationship between flavor conserving dipole moments, such as the magnetic and the electric dipole moments, and flavor violating dipole moments, such as and , is quite different from that in the MSSM. From general analytic considerations, we derive bounds on the fractional sneutrino mass splittings , and the fractional charged slepton splittings . For , the mixing is allowed to be maximal. We also comment on the magnitudes and correlations between CP-violating angles coming from electric dipole moments. We supplement the analytical considerations by detailed numerical calculations. Received: 6 September 2001 / Revised version: 30 October 2001 / Published online: 7 December 2001     

Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots

Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.     

Forbidden ESR transitionsΔS = ±2 of Fe3+ and Mn2+ in zinc oxide

Forbidden ESR transitions were investigated at 9 GHz in zinc oxide doped with Fe³⁺ and Mn²⁺. The crystal field parameters were determined by means of a computer program. Furtheron, the splittings of the lines for general orientations of the crystal axes relative to the magnetic field were calculated.     

Structure and symmetry of azulene as determined from microwave spectra of isotopomers

The rotational spectra of six ¹³C isotopomers in natural abundance and of eight synthesized deuterium isotopomers of azulene have been measured using pulsed nozzle cavity and waveguide Fourier transform microwave (FTMW) spectrometers over the 8–18?GHz range. The spectrum of the parent species was remeasured with the higher resolution of FTMW spectrometers. Rotational constants have been fitted to the measured frequencies of the rotational transitions of all measured isotopomers. In addition, centrifugal distortion constants were determined for the parent species and the deuterated isotopomers. The permanent electric dipole moment was redetermined from Stark splittings. The C_2v covering symmetry of the azulene molecule has been demonstrated unambiguously from a single set of observed transitions for the asymmetrically substituted 1-, 4-, 5- and 9-¹³C–isotopomers at twice the intensity of the symmetrically substituted 2- and 6-¹³C–isotopomers. The positions of all nuclei of the planar non–alternating aromatic ring system of azulene have been determined from moments of inertia of all available isotopomers. Different methods have been used to arrive at a near equilibrium structure.     

The microwave spectrum and dipole moment of heptafulvene

The microwave spectrum of heptafulvene (C₈H₈) has been investigated in the frequency range from 26 to 40 GHz. The following rotational constants have been obtained from a least-squares fit of the measured transition frequencies: A = 3665.972(66)MHz, B = 2004.3165(59)MHz, and C = 1297.5029(90)MHz. From the corresponding moments of inertia it was concluded that heptafulvene has a planar equilibrium structure. The quantitative measurement of the Stark splittings of three transitions have yielded a dipole moment of 0.477(5) D along the a principal axis. A series of satellite transitions accompanied each rotational transition. The satellites have been assigned to the lowest out-of-plane vibration ν₄₂ (B₂) for which a frequency of 70(11) cm^?1 has been determined from relative intensity measurements.     

Determination of the242m Am nuclear moments

The hyperfine structure of Am atoms was investigated in an atomic beam by laser spectroscopy. The observed splittings were evaluated with respect to the magnetic dipole and electric quadrupole moments of^242m Am. The results are: μ _I (^242m Am)=+0.97(5)nm,Q(^242m Am)=+6.5(2.0)b.     

铯原子里德堡态Stark能量及电偶极矩的测量和理论计算

里德堡原子由于具有体积大、寿命长、易极化及在外电场中能级易于操控等特点, 已经成为了目前物理学领域研究的热点之一. 本文在磁光阱中实验测量了铯原子15P_3/2和16P_3/2态的Stark光谱,根据光谱给出了15P_3/2和16P_3/2|m|=1/2 Stark态在0-1400 V/cm场强范围适用的Stark 能量和偶极矩的经验性解析表达式; 用数值方法求解薛定谔方程获得了这些态的Stark能量、偶极矩和电子几率密度分布. 电子几率密度分布定性说明了计算的偶极矩矢量的方向是正确的. 计算的Stark能量、偶极矩与实验结果相一致.     

Measurement of the electric dipole moment of NO (X2 Π ν = 0,1) by mid-infrared laser magnetic resonance spectroscopy

A pair of parallel Stark plates are added to a CO laser magnetic resonance spectrometer to apply electric field in the absorption cell. This apparatus is used to measure the molecular electric dipole moment via Zeeman and Stark effects simultaneously. The saturated absorption spectra of NO (X²Π_3/2, ν = 1 ← 0) was observed and the electric dipole moments of NO were directly measured in the presence of an electric field. The dipole moments are determined as μ₀(ν = 0) = 0.1595(15) D, μ₁ (ν = 1) = 0.1425(16) D. The electric dipole moment of the vibrationally excited state (ν = 1) is determined for the first time. The dependence of the electric dipole moments on its nuclear distances is interpreted.     

Rotational Spectrum, Hyperfine Structure, and Internal Rotation of Methyl Carbamate

Methyl carbamate, an isomer of glycine, is a possible candidate for interstellar detection. It might be more abundant than glycine and its dipole moment is much larger. Furthermore, using high-level quantum chemical calculations, it is shown that syn methyl carbamate has a lower energy than glycine. The quadrupole hyperfine structure due to ¹⁴N has been measured using microwave Fourier transform spectroscopy. The rotational spectrum of the ground vibrational state has been measured from 8 to 240 GHz and accurate spectroscopic constants have been determined for the A internal rotation components of the rotational lines. Finally, the internal rotation splittings have been analyzed.     

Wave-particle duality of solitons and solitonic analog of the Ramsauer-Townsend effect

We study the interaction of light beams carrying angular momentum with a single, trapped and well localized ion. We provide a detailed calculation of selection rules and excitation probabilities for quadrupole transitions. The results show the dependencies on the angular momentum and polarization of the laser beam as well as the direction of the quantization magnetic field. In order to optimally observe the specific effects, focusing the angular momentum beam close to the diffraction limit is required. We discuss a protocol for examining experimentally the effects on the S_1/2 to D_5/2 transition using a ⁴⁰Ca⁺ ion. Various applications and advantages are expected when using light carrying angular momentum: in quantum information processing, where qubit states of ion crystals are controlled, parasitic light shifts could be avoided as the ion is excited in the dark zone of the beam at zero electric field amplitude. Such interactions also open the door to high dimensional entanglement between light and matter. In spectroscopy one might access transitions which have escaped excitation so far due to vanishing transition dipole moments.     

Zero field splittings of Gd3+IN Nd2(SO4)3 · 8H2O and Sm2(SO4)3 · 8H2O crystals at 273 K

The electron paramagnetic resonance (EPR) of Nd₂(SO₄)₃ · 8H₂O and Sm₂(SO₄)₃ · 8H₂O doped with Gd³⁺ has been carried out at 273 K and the spin-Hamiltonian parameters are deduced. The zero field splittings have been computed and compared with those observed directly by Bogle and Symmons. It is found that the discrepancy in the zero field splittings. between computed and directly observed values falls within the range of linewidths of directly observed values.     

On the mechanism of electromagnetic microwave absorption in superfluid helium

In experiments on electromagnetic (EM) wave absorption in the microwave range in superfluid (SF) helium [1?C3], a narrow EM field absorption line with a width on the order of (20?C200) kHz was observed against the background of a wide absorption band with a width of 30?C40 GHz at frequencies f ₀ ?? 110?C180 GHz corresponding to the roton gap energy ?? _r (T) in the temperature range 1.4?C2.2 K. Using the so-called flexoelectric mechanism of polarization of helium atoms (⁴He) in the presence of density gradients in SF helium (HeII), we show that nonresonance microwave absorption in the frequency range 170?C200 GHz can be due to the existence of time-varying local density gradients produced by roton excitations in the bulk HeII. The absorption bandwidth is determined by the roton-roton scattering time in an equilibrium Boltzmann gas of rotons, which is t _r-r ?? 3.4 × 10^?11 s at T = 1.4 K and decreases upon heating. We propose that the anomalously narrow microwave resonance absorption line in HeII at the roton frequency f ₀(T) = ??r(T)/2??? appears due to the following two factors: (i) the discrete structure of the spectrum of the surface EM resonator modes in the form of a periodic sequence of narrow peaks and (ii) the presence of a stationary dipole layer in HeII near the resonator surface, which forms due to polarization of ⁴He atoms under the action of the density gradient associated with the vanishing of the density of the SF component at the solid wall. For this reason, the relaxation of nonequilibrium rotons generated in such a surface dipole layer is strongly suppressed, and the shape and width of the microwave resonance absorption line are determined by the roton density of states, which has a sharp peak at the edge of the roton gap in the case of weak dissipation. The effective dipole moments of rotons in the dipole layer can be directed either along or across the normal to the resonator surface, which explains the experimentally observed symmetric doublet splitting of the resonance absorption line in an external dc electric field perpendicular to the resonator surface. We show that negative absorption (induced emission) of EM field quanta observed after triggering a Kapitza ??heat gun?? occurs when the occupation numbers for roton states due to ??pumping?? of rotons exceed the occupation numbers of EM field photons in the resonator.     

Charge radii and moments of strontium nuclei by laser spectroscopy

The isotope shifts and hyperfine splittings for 11 strontium isotopes (A=80–90) and two isomers for the optical transition λ=293.2 nm were measured. The magnetic dipole and electric quadrupole moments and the changes of the mean square charge radii are derived. The results are discussed with respect to the increasing nuclear deformation and the anomalous coupling scheme of light Sr nuclei.     

外电场对对硝基氯苯分子结构与电子光谱影响的研究

为达到降解有机污染物硝基氯苯的目的, 采用外加平行电场的方法, 研究电场对硝基氯苯化合物的分子结构和电子光谱等的影响. 以对硝基氯苯分子为研究对象, 采用密度泛函B3LYP方法在6-311+g(d, p) 基组水平上优化并计算了不同外电场作用下pCNB的基态分子结构、电偶极矩和分子总能量, 在此基础上采用含时密度泛函研究了该分子的前六个激发态的波长、振子强度受外电场的影响规律.结果表明: C–Cl, C–N键长随电场增加而快速增大, 即键能快速减小, 同时苯环上的C–C, C–H键长的变化很小, 且有增有减, 说明分子的降解可能是C–Cl, C–N键断裂而苯环则相对稳定. 同时分子总能量随电场先增大后变小, 电偶极矩刚好相反.另外, 最大吸收波长λ_max 随电场先缓慢减小, 后快速增大, 导致电子跃迁相对容易, 而振子强度随电场变化则相对比较复杂. 关键词： 对硝基氯苯 外电场 密度泛函 含时密度泛函     

A comparison of effective and polarizable intermolecular potentials in simulations: liquid water as a test case

A comparison of polarizable and effective intermolecular potentials has been carried out by employing simulated properties of liquid water at different temperatures. The effective potentials were obtained by adding a fixed fraction (~80%) of the induced dipole moments of the polarizable potential to the permanent dipole moment of the water molecule. The fraction was fitted to reproduce one structural (the height of the first peak of the oxygen-oxygen radial distribution function) and one dynamic (the self-diffusion coefficient) liquid property predicted by the polarizable potential. The two properties were well reproduced simultaneously by the effective potential at 273 K and 303 K, but less accurately at 373 K. The effective dipole moments were 2.79, 2.75, and 2.68 D at the three respective temperatures. In order to examine the effective potentials further, other liquid properties have been considered, and we found that the molecular rotational relaxation times and the hydrogen bonding properties are reproduced well by the effective potentials, whereas the velocity autocorrelation function, the pressure, the dielectric constant, and the Debye relaxation time are reproduced less accurately.