Laser Stark saturation spectroscopy in methyl alcohol

The method of Lamb dip spectroscopy in Stark tuned molecular gases is discussed and applied to the experimental assignment of methyl alcohol infrared transitions in the ₅ C–O stretch band. Theoretical expressions for Stark Lamb dip patterns are derived for P, Q and R-branch transitions. Stark tuning results and transition quantum number assignments are presented for several 10m transitions, along with measured values of resonant frequencies, absorption coefficients and pressure broadening coefficients.Work supported by the Army Research Office, Durham, and the National Science Foundation.     

Spectral holeburning and the Stark and Zeeman effects in SrF2:Sm2+

We have observed narrow (40 MHz) persistent spectral holeburning in SrF₂:Sm²⁺ for Sm²⁺ ions in perturbed cubic sites. The transition studied is ⁷F₀?⁵D₀ between the f-electron states. Stark effect measurements show a linear splitting with a coefficient of 0.006 MHz/V cm^-1 and the splitting pattern shows that the site has C_4V symmetry. The C_4V perturbation is very weak and leads to unresolved splittings of cubic T_1g levels of ～2 cm^-1. The nonlinear Zeeman effect was studied using holeburning and the coefficient of 1.04 Hz/G² shows that the predominant magnetic coupling is in the ground state as found recently for CaF₂:Sm²⁺.     

Internal rotation in methyl silane by avoided-crossing molecular-beam spectroscopy

The avoided-crossing molecular-beam electric-resonance technique was applied to methyl silane in the ground torsional state. A new type of anticrossing is introduced which breaks the torsional symmetry and obeys the selection rules ΔJ = 0, K = +1 /a3 ?1. For these “barrier” anticrossings, the values of the crossing fields E_c yield directly the internal rotation splittings; the E_c are independent of the difference (A-B) in the rotational constants. Such anticrossings were observed for J from 1 to 6. Studies were also conducted of several “rotational” anticrossings (J, K) = (1, ±1) /a3 (2, 0) for which E_c does depend on (A-B). The normal rotational transition (J, K) = (1, 0) ← (0, 0) was observed in the ground torsional state using the molecular beam spectrometer. The present data on CH₃²⁸SiH₃ were combined with Hirota's microwave spectra and analyzed with the torsion-rotation Hamiltonian including all quartic centrifugal distortion terms. In addition to evaluating B and several distortion constants, determinations were made of the moment of inertia of the methyl top I_α = 3.165(5) amu-Ų, the effective rotational constant A^eff = 56 189.449(32) MHz, and the effective height of the threefold barrier to internal rotation V₃^eff = 592.3359(73) cm^?1. The correlations leading to these two effective constants are discussed and the true values of A and V₃ are determined within certain approximations. For the isotopic species CH₃³⁰SiH₃, barrier and rotational anticrossings were observed. The isotopic changes in A and V₃ were determined, as well as an upper limit to the corresponding change in I_α.     

The vibration-internal rotation-overall rotation interactions in the symmetric-top molecules: The microwave spectrum of methyl silane

Laurie's theory on the coupling between internal rotation and a degenerate vibration in a symmetric-top molecule is examined by investigating the microwave spectra of methyl silane and methyl silane-d₃ in the ν₁₂ and ν₆ + ν₁₂ states. Two sets of l-type doublets are observed in the J = 2 ← 1, K = 1 transitions; however, the observed frequencies as well as the Stark effects of the l-type doublets indicate definitely that Laurie's expressions for the l-type doublets are to be revised. It is shown theoretically that Coriolis couplings remove discrepancy between theory and experiment; when A₁ and A₂ denote the rotational constants of CH₃ and SiH₃ about the symmetry axes and ζ₁ and ζ₂ measure the magnitudes of angular momenta induced by the ν₁₂ vibration in the two tops, experimental results require that (−A₁ζ₁ + A₂ζ₂) is 104 950-107 048 MHz and 45 214-47 626 MHz for CH₃SiH₃ and CH₃SiD₃, respectively.     

Application of the contact transformation method to torsional problems in methyl silane

The effect of the torsional degree of freedom on redundancies in the Hamiltonian and on the dipole operator has been investigated for methyl silane-like molecules. By applying a rotational contact transformation to the torsion-rotation Hamiltonian H_TR for the ground vibrational state, a systematic method is demonstrated for treating the redundancies that relate different terms in H_TR. In general, with this method, the experimentally accessible molecular parameters in the reduced Hamiltonian can be related to the physically significant molecular parameters in the untransformed Hamiltonian. It is shown that H_TR contains a new term which has matrix elements with selection rules (ΔK = ±3), (Δσ = 0), and Δv_T arbitrary, where v_T and σ label the torsional levels and sublevels, respectively. As a result of this term, the distortion dipole constant μ_D which characterizes (ΔK = ±3) matrix elements in C_3v molecules cannot, in systems like CH₃SiH₃, be ascribed entirely to centrifugal distortion but can contain a significant contribution from torsional effects. Furthermore, new transitions can appear in the pure torsional bands which may be strong enough to observe in low barrier molecules. By applying a vibrational contact transformation, the form is derived of the leading torsional terms in the dipole moment expansion. The four dipole distortion constants μ₀^T, μ₂^T, μ_|;^T, and μ_Λ^T which characterize these terms are related to the molecular parameters that enter the Coriolis, centrifugal distortion, and anharmonicity contributions to the vibration-torsion-rotation Hamiltonian.     

Non-linear effects in a molecular beam Zeeman maser oscillator

The flux of lower state molecules emerging from the cavity of an almost phase locked biharmonic ammonia maser oscillator is found to be amplitude modulated at the biharmonic beat frequency. This molecular state modulation is attributed to periodic pulling phenomena.     

The dipole moment of water: Stark effects in D2O and HDO

The dipole moment of D₂O has been determined from Stark effect measurements for the 3₁₃–2₂₀ and 4₄₁–5₃₂ microwave transitions as 1·857 ± 0·006 and 1·869 ± 0·005D respectively. A rotational dependence of dipole moment has also been established for HDO through μ_a in the 2₂₀–2₂₁ and 5₃₂–5₃₃ transitions; μ_a was determined as 0·662 ± 0·001 and 0·644 ± 0·001D respectively. The total dipole moment for HDO has been determined from the 3₂₁–4₁₄ transition to be 1·85 ± 0·01D and to lie within 0·1° of the bisector of the HOD angle. High resolution Stark spectroscopy has been performed on the 6₂₄–6₁₅ transition of D₂O with improved precision using the 337 μm emission line of the HCN laser. This experiment has confirmed the dipole results from the microwave work and the frequency of the 6₂₄–6₁₅ transition in D₂O has been determined as 890 395 ± 3 MHz.

The slight increase of dipole moment with deuteration is consistent with the dipole moment for H₂O determined from the dielectric constant. This increase is discussed for the vibrational ground state (as for ammonia) in terms of anharmonicity in the bending vibration. The change of μ with rotational transition is interpreted in terms of large changes in molecular geometry for certain rotational states due to centrifugal distortion.     

The Zeeman effect revisited

We announce three new rigorous results for the quantum mechanical hydrogen atom in constant magnetic field: (i) Borel summability of the small field perturbation series, (ii) detailed large field asymptotics, and (iii) non-degeneracy of the ground state Ω₀ and a proof that it has $\text{L}{}_{\mathrm{z}}\text{Ω}{}_0\text{= 0}$ for all values of the field.     

Curvature and Zeeman effects on persistent currents in a multi-walledcarbon nanotorus

Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown that in the absence of the Zeeman effect, the intrinsic curvature induces some dramatic changes in energy spectra and thus changes in the shape of the flux-dependent current. A paramagnetism--diamagnetism transition is observed. With consideration of the Zeeman splitting energy, the period of persistent current is destroyed, and a diamagnetism--paramagnetism transition is obtained at high magnetic field. In addition, we further explore the effect of external electric field energy (E_ef) on persistent current, indicating that it changes unmonotonously with E_ef.     

The vibrational Zeeman effect

The theory of the vibrational Zeeman effect in symmetric top molecules is presented. It is shown that vibrational g factors may be related to rotational g factors and estimates are made of their magnitude for a number of molecules; these calculations indicate that vibrational Zeeman effects should be observable in symmetric top molecules in degenerate vibrational states. In addition, the novel features of the theory for linear molecules are discussed.     

不同微场分布函数对Stark加宽和频移的影响

分别采用Holtsmark,Neutral Point,Nearest-Neighbor和Mayer模型微场分布函数对Stark线型进行了研究,进而得到相应微场函数下的Stark加宽和频移,研究了4种不同的微场分布函数对Stark加宽和频移的影响。研究结果表明,在电子加宽参数不变时,4种微场分布函数对Stark加宽和频移的影响随离子加宽参数的增加而增加;在离子加宽参数不变时,4种微场分布函数对Stark加宽和频移的影响随电子加宽参数的增加而增加;特别是,当离子加宽参数较大时,Mayer模型微场分布函数对Stark加宽和频移的影响异常明显。这说明,微场分布函数对谱线的加宽和频移的影响在离子与离子碰撞剧烈的等离子体环境中尤其显著, 在这样的等离子体环境中,进行等离子体诊断时,选择合适的微场分布函数非常重要。结果对等离子体诊断有一定参考价值。     

The Covariant Stark Effect

This paper examines the Stark effect, as a first order perturbation of manifestly covariant hydrogen-like bound states. These bound states are solutions to a relativistic Schrödinger equation with invariant evolution parameter, and represent mass eigenstates whose eigenvalues correspond to the well-known energy spectrum of the nonrelativistic theory. In analogy to the nonrelativistic case, the off-diagonal perturbation leads to a lifting of the degeneracy in the mass spectrum. In the covariant case, not only do the spectral lines split, but they acquire an imaginary part which is linear in the applied electric field, thus revealing induced bound state decay in first order perturbation theory. This imaginary part results from the coupling of the external field to the non-compact boost generator. In order to recover the conventional first order Stark splitting, we must include a scalar potential term. This term may be understood as a fifth gauge potential, which compensates for dependence of gauge transformations on the invariant evolution parameter.     

Combined Aharonov-Bohm and Zeeman spin-polarization effects in a double quantum dot ring

A mesoscale Aharonov-Bohm (AB) ring with a quantum dot (QD) embedded in each arm is computationally modeled for unique transmission properties arising from a combination of AB effects and Zeeman splitting of the QD energy levels. A tight-binding Hamiltonian is solved, providing analytical expressions for the transmission as a function of system parameters. Transmission resonances with spin-polarized output are presented for cases involving either a perpendicular field, or a parallel field, or both. The combination of the AB-effect with Zeeman splitting allows sensitive control of the output resonances of the device, manifesting in spin-polarized states which separate and cross as a function of applied field. In the case with perpendicular flux, the AB-oscillations exhibit atypical non-periodicity, and Fano-type resonances appear as a function of magnetic flux due to the flux-dependent shift in the QD energy levels via the Zeeman effect.     

Observation of Zeeman degeneracy effects in collisional intense field resonance fluorescence

We report observation of the scattered spectrum from a Zeeman degenerate atom at high laser intensities. For a J = 0 to J = 1 transition in the presence of collisions we observe an asymmetric triplet in the polarization parallel to the incident laser and an asymmetric doublet in the polarization perpendicular to the incident laser.     

Zeeman and spin–orbit effects on the spin-Hall conductance

We show that when a two-dimensional interacting electron gas is submitted to a perpendicular magnetic field, the application of an in-plane electric field E induces a spin current perpendicular to E whose conductivity is quantized. This current can lead to spin accumulation that might be detected by means of optical experiments. The appearance of this intrinsic spin-Hall effect is crucially based on the validity of Kohn's theorem and on the presence of the Zeeman term in the electron Hamiltonian. The possibility of resonant effects in the spin-Hall conductivity due to the combined effect of Rashba and Dresselhaus spin–orbit couplings is discussed.     

The Zeeman effect for helium atom

The g-factors of the 23P, 21P, and 33P states of the helium atom are calculated by using the vatiational wave functions constructed from the linear combinations of Slater-type basis sets. The relativistic corrections to order α2(a.u.) and the effect of the motion of the center of mass are treated by using first-order perturbation theory. Most of our predicted results are in good agreement with recent results of Yan and Drake, which were obtained by using the wave functions with doubled Hylleraas coordinates. Based on the analysis of the convergence pattern in our calculation, we believe that our predicted value of the δgL-factor for 33P state in 4He, 2.914 15×10-7, ought to be reasonable and accurate, although there are no corresponding experimental data available in the liteature yet to be compared with.