Determination of the distribution function of Stark dipole moments induced by a matrix in amorphous impurity systems

The burning kinetics of closely spaced equidistant holes in impurity absorption spectra of glasses and polymers is theoretically studied in an alternating electric field (alternating in the magnitude, sign, and direction). The height of barriers between wells of the burnt multiwell spectral hole depends on the shape of the distribution of impurity molecules over the Stark dipole moments. Centrally symmetric impurity molecules are considered whose Stark moment is determined exclusively by the interaction with matrix molecules. Model calculations performed for different hypothetical distribution functions of Stark moments yield substantially different kinetics. Therefore, the method described allows one to verify experimentally various hypotheses about the nature of matrix-induced Stark moments.     

Optical fractionation of an ensemble of impurity molecules over the magnitude of a Stark moment induced by an amorphous matrix

A method of selective (with respect to the Stark effect) burning of a spectral hole in the 0-0 absorption band of zero-dipole impurity molecules is suggested. It is shown that in combination with the Stark modulation of the optical density of a sample, this method makes it possible to determine that contribution to the total absorption and luminescence of the sample that the impurity molecules with a preset magnitude of the matrix-induced Stark moment (provided this magnitude exceeds the mean value for the entire ensemble) make. This allows one to experimentally study both the distribution of impurity molecules over the magnitude of the Stark moment and the correlation of the Stark moment with other parameters of impurity molecules.     

Photoselection of impurity molecules with respect to the orientation of their stark moments induced by an amorphous matrix

A method of selective (relative to the magnitude of the linear Stark effect in zero-dipole impurity molecules) burning of holes in the spectra of amorphous matrices is studied. It is shown that this method makes it possible not only to select a subensemble of impurity molecules having both preset energy of the 0-0 transition and magnitude of the matrix-induced Stark moment, but also to divide this subensemble into two fractions whose Stark moments are predominantly oriented either along the transition moment or perpendicular to it. The possibility of experimental verification of the most popular hypothesis about the origin of induced Stark moments, which neglects a possible correlation between the direction of the Stark moment and that of the transition dipole moment, is considered. The method described also allows one to study experimentally the correlation of some other photophysical parameters of impurity molecules with the direction of local internal fields relative to the vector of the transition dipole moment.     

Theory of higher-order stark effect of symmetric top molecules

The Stark effect formula for symmetric top molecules, which is correct to the fifth order of an external electric field, is given. The formula is applicable to linear molecules without or with electronic angular momenta coupled in Hund;s case a. Numerical tables are given for the special case of linear molecules without any electronic angular momentum. The effect of centrifugal stretching is considered to the first order. It is shown that our perturbation formula, which is correct to the sixth order of an external electric field, is good even when μE/B is about 1.     

Photoselection of impurity molecules in amorphous media over the zero-phonon linewidth

The shape of a multiwell hole, which is produced upon burning a number of closely spaced equidistant spectral holes in the low-temperature absorption spectrum of an impurity amorphous solid, is studied. When the bottom of such a hole is probed by the wavelength-modulated light, the transmission and luminescence of the sample become modulated. This modulation is caused by a subsystem of impurity molecules, which differs from a total ensemble by a smaller scatter in the zero-phonon linewidth and a smaller (by a factor of 2–3) mean value of this width. The study of the photophysical parameters of this subsystem can yield useful information for simulating the nanostructure of an amorphous body.     

Electronic structure of GaAs/AlGaAs quantum double rings in lateral electric field

A three-dimensional model of GaAs/A1GaAs quantum double rings in the lateral static electric field is investigated theoretically.The eigenvalue problem with the effective-mass approximation is solved by means of the finite-element method.The energy levels and wave functions of quantum-confined electrons and heavy holes are obtained and show an agreement with our previous theoretical and experimental studies.It is shown in the approximation of neglecting the Coulomb attraction between the electron and heavy hole that a relatively large Stark shift of exciton emission of 4 meV is attainable with an applied electric field of 0.7 kV/cm.     

Influence of strain on the Stark effect in InP/GaInP quantum discs

In InP/GaInP quantum discs it is shown that strain induces a type I to type II transition with increasing thickness of the disc. When an external electric field is applied along the cylindrical axis of the disc, the exciton energy exhibits a Stark effect, which for the light hole exciton becomes linear even for a small field value, while for the heavy hole it is more quadratic.     

Electric-field control of electron–hole wave functions in a wide quantum well

The electric field dependence of the electron/hole wave function and the radiation energy of an exciton in a Be-δ-doped 80 nm quantum well (QW) is studied experimentally and compared it with variational calculation. The photoluminescence (PL) spectra show Stark shifts depending on the gate electric field and PL intensity of the exciton of the first excited state has a dip in the electric-field dependence which reflects the node of the electron wave function.     

Optical fractionation of an ensemble of impurity molecules with respect to the magnitude of the piezochromic effect

A method of hole burning in the 0-0 band of the impurity-absorption spectra of polymers and glasses is suggested. This method is selective not only with respect to the transition energy, but also with respect to the magnitude of the piezochromic effect. It is shown that, in combination with the modulation of the wavelength of probe radiation, this method makes it possible to determine the contribution of the impurity molecules with a specified magnitude of the piezochromic effect to the total absorption and luminescence of a sample. This circumstance allows one to study experimentally the correlation of the piezochromic effect with other characteristics of impurity molecules.     

Bremsstrahlung of a neutral fermi particle in the field of a plane electromagnetic wave

The bremsstrahlung is considered from a neutral Fermi particle with anomalous magnetic and electric moments in the field of a screened Coulomb center and in the presence of a plane electromagnetic wave. The effect of the wave polarization on the scattering cross section and the behavior of the particle spin during the scattering process are considered. Cross sections are given for scattering of a particle at a Coulomb center in the presence of constant, crossed electric and magnetic fields which are equal in magnitude and also for a free particle. It is shown that the effect of the anomalous electric moment is often decisive.     

Hole burning spectroscopy with preliminary photoselection of impurity molecules

The photoselection of impurity molecules caused by spectral hole burning produces a specific spectral angular distribution of the molecules in low-temperature amorphous matrices: All the molecules, whose zero-phonon absorption lines lie within a selected narrow spectral interval, have a specified distribution of their orientations relative to the laboratory coordinate system. In this paper, the possibility of application of known methods of hole burning in this spectral interval is studied and the outlook for combination of these methods with preliminary photoselection is demonstrated by the example of the Stark effect.     

Dipole moments of molecules solvated in helium nanodroplets

Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium.     

Stark effect of adsorbate vibrations

The theory of the vibrational Stark effect of adsorbates is discussed. In particular, the reported linear variation of CO vibrational frequency with potential difference across the Pt-electrolyte interface is shown to be consistent with a recent measurement of the Stark tuning rate of CO on Ni [110] in UHV and the differential capacitance of the Pt-electrolyte interface. We also demonstrate that the Stark tuning rate of CO on Ni [110] is itself in agreement with theoretical prediction. Our vibrational Hamiltonian applies to atomic adsorbates and molecules. It relates frequency shifts of the adsorbate to the local electric field at an adsorbate free surface.     

Stark shift and dissociation process of an ionized donor bound exciton in spherical quantum dots

The effect of an electric field on the ground state energy of an exciton bound to an ionized donor (D⁺, X) was studied in CdSe spherical quantum dots where quantum confinement is described by an infinitly deep potential. Calculations have been performed in the framework of the effective mass approximation using a variational method by choosing an appropriate sixty-terms wave function taking into account different interparticles correlations and symetry distorsion induced by the electric field. It appears that the Stark shift is significant even for low fields and depends strongly of spherical dot sizes. The competition between the confinement effect and the Stark effect is discussed as function of the spherical dot size and the applied electric field strength. The (D⁺, X) Stark shift is estimated and its behavior is discussed as a function of the dot radius and electric field strength. The electron and hole average distances have also been calculated and the role of the ionized donor in the excitonic dissociation is established.     

New all-optical method for measuring molecular permanent dipole moment difference using two-photon absorption spectroscopy

Stark effect, in combination with spectral hole burning and single-molecule spectroscopy, has been a fruitful technique to study permanent electric dipole moment of molecules in condensed phase. However, because measuring Stark shifts relies on external fields and narrow line- or hole-widths, the applicability of this method at ambient conditions required by most biological systems has remained limited. Here we demonstrate a new all-optical method for measuring the molecular dipole moment difference between ground and excited states using two-photon absorption (2PA) spectroscopy. We show that the value and orientation of the static dipole moment difference can be determined from the corresponding absolute 2PA cross-section. We use this new method to determine for the first time the strength of local electric field E_loc=0.1-1.0×10⁸ V/cm inside beta-barrel of Fruit series of red fluorescent proteins. Because our method does not rely on external field and is applicable in liquid solutions, it is well suited for the study of biological systems.     

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.     

调制n型掺杂ZnSe/BeTe Ⅱ型量子阱结构的发光特性

报道了调制n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-II QW)在极低温至室温(14—296K)条件下的各种光学性质. 反射光谱显示了对于非掺杂样品,激子(X)的跃迁起着支配作用,而只有在掺杂样品的光谱里展示了一个典型的负的带电激子(X^-)的跃迁特征. PL光谱及其直线偏振度P_l都显著地依赖于n型掺杂量和平行于QW生长方向的外加电场. 这个特征被认为是由n型掺杂导致了内秉电场(built 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱     

Quantum-Confined Stark Effects in a Single GaN Quantum Dot

Using analytical expressions for the polarization field in GaN quantum dot, and an approximation by separating the potential into a radial and an axial, we investigate theoretically the quantum-confined Stark effects. The electron and hole energy levels and optical transition energies are calculated in the presence of an electric field in different directions. The results show that the electron and hole energy levels and the optical transition energies can cause redshifts for the lateral electric field and blueshifts for the vertical field. The rotational direction of electric field can also change the energy shift.