共查询到20条相似文献,搜索用时 62 毫秒
1.
General expressions used for transforming raw laser-induced fluorescence (LIF) intensity into the population and alignment parameters of a symmetric top molecule are derived by employing the density matrix approach. The molecular population and alignment are described by molecular state multipoles. The results are presented for a general excitation-detection geometry and then applied to some special geometries. In general cases, the LIF intensity is a complex function of the initial molecular state multipoles, the dynamic factors and the excitation-detection geometrical factors. It contains a population and 14 alignment multipoles. How to extract all initial state multipoles from the rotationally unresolved emission LIF intensity is discussed in detail. 相似文献
2.
We demonstrate experimentally an atomic magnetometer based on optical pumping theory, a magnetic resonance that is induced by a radio frequency field and dependent on the magnetic field strength. Compared with the conventional method using one radiation field, which is used not only as the probe beam but also as a pump beam, the additional re-pump beam can increase remarkably the amplitude of the signal. It is shown that the amplitude of the magnetic field resonance signal can increase more than 55% by using an additional re-pump beam, which makes the sensitivity of the magnetometer higher. Finally, we investigate the relation between amplitude of the signal and re-pump laser power, and calculate the atomic population in the trapping states with rate equations. 相似文献
3.
Fabio J. Mazzotti Lizandra Barrios Ranjini Raghunandan John P. Maier 《Molecular physics》2013,111(2):335-344
Theoretical quantitative considerations as well as experimental data are presented based on absorption population depletion coupled with cavity ringdown spectroscopy. The absorbing number densities inside the cavity are determined by numerical integration of the coupled rate equations. The number of photons involved in absorption, cavity losses due to mirror reflectivity and stimulated emission are taken into account. The principle is to monitor a first transition by cavity ringdown spectroscopy while a second transition, with a state in common, is resonantly excited by the decaying radiation of different frequency also trapped inside the optical cavity. A numerical example is given for atomic lines of neon and the measurements carried out in a supersonic slit-jet expansion discharge demonstrate the feasibility of the technique. The technique is also proven to work with two resonant transitions of C2. Translational velocity of the jet modifying the rate equations is included in the model. 相似文献
4.
Aleksandra Foltynowicz 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,108(2):220-238
A theoretical investigation of the influence of optical pumping on wavelength modulation absorption spectrometry (WMAS) signals from collision broadened atoms and molecules is presented. General expressions for the nf-WMAS signal from atomic and molecular systems, modeled as three-level systems that can accommodate both optical saturation and optical pumping, are derived by the use of a previously developed Fourier series-based formalism in combination with rate equations solved under steady-state conditions. The expressions are similar to those describing the nf-WMAS signal from two-level systems that can accommodate optical saturation [Schmidt FM, Foltynowicz A, Gustafsson J, Axner O, WMAS from optically saturated collision-broadened transitions. JQSRT 2005;94:225-54], the difference being the value of the saturation flux, wherefore the general parametric dependence of WMAS signals from optically pumped systems is the same as that from optically saturated systems. The additional effect of optical pumping on the WMAS signal is investigated for three typical cases: molecules or atoms in an ordinary atmosphere, atoms in an inert atmosphere, and atoms or molecules possessing metastable states. The possibility to describe any of these systems with a two-level model is investigated. 相似文献
5.
L. G. Si W. X. Yang X. Y. Lü J. H. Li X. X. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):161-166
The authors show the formation of slow temporal vector
optical solitons in a cold lifetime-broadened four-level inverted-Y
atomic system. We demonstrate that Maxwell’s equations for
describing two orthogonally polarised components of a low intensity
signal field can evolve into two coupled nonlinear Schr?dinger
equations, which results in various distortion-free temporal vector
optical solitons, such as bright-bright or dark-dark vector
solitons. These results are produced from the correct balance
between dispersion, self- and cross-phase modulation (SPM and XPM)
effects. We also show that the integrable Manakov model can be
realised by adjusting the corresponding SPM, XPM and dispersion
effects of this inverted-Y atomic system. 相似文献
6.
David J. Butcher 《应用光谱学评论》2013,48(6):543-562
Abstract Lasers have advantages compared to conventional light sources, which include high power, a monochromatic emission profile, stability, and rapid tuning across an atomic line. These advantages have resulted in superior analytical figures of merit and methods of background correction compared to conventional light sources. The most widely used lasers for atomic spectrometry include dye laser systems, optical parametric oscillator systems, and diode lasers. Three principal techniques employ lasers as light sources. Laser‐excited atomic fluorescence spectrometry (LEAFS) involves the use of laser light to excite atoms that emit fluorescence and serves as the analytical signal. Laser‐enhanced ionization (LEI) involves laser excitation of atoms to an excited state energy level at which collisional ionization occurs at a higher rate than from the ground state. Diode laser atomic absorption spectrometry (DLAAS) employs a DL as a source to excite atoms in an atom cell from the ground state to an excited state. The analytical signal is involves the ratio of the incident and transmitted beams. Recent applications of these techniques are discussed, including practical applications, hyphenated techniques employing laser‐induced plasmas, and work to characterize fundamental spectroscopic parameters. 相似文献
7.
T.T. Gien 《Physics letters. A》1982,92(9):435-438
The relationship between the integral alignment and orientation coefficients and the polarizations of the decay photons measured in an experiment where the scattered electrons are not observed is expounded. The determination of some integrated state multipoles is shown to provide also a simple checking of the plane symmetry invariance of an atomic collision. 相似文献
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E. A. Gazazyan G. G. Grigoryan A. V. Papoyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2011,46(4):145-149
Amplification of a weak circularly polarized light signal in a multilevel atomic medium excited by a strong linearly polarized
resonant radiation is studied. A strong optical pumping may lead to the population inversion between magnetic sublevels of
hyperfine components of the ground and excited states. Solution to the self-consistent system of density matrix equations
and Maxwell equations for propagation of the weak signal allows analyzing optimum conditions of amplification. 相似文献
10.
A. Godone F. Levi S. Micalizio J. Vanier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):5-13
An analysis of the phenomenon of coherent population trapping as observed by means of the dark state in the case of optically
thick vapors in alkali metal atoms is presented. Very different behaviors are predicted for the observation of the dark state
in the fluorescence and transmission spectra of the same atomic sample when the optical length is not negligible. Among other
effects, the dark line observed in the fluorescence signal may look inverted appearing as a bright line, while in the transmission
signal a narrowing of the line width resonance line is observed for an increase of the atomic density. In the pure three-level
scheme a subnatural width is predicted. These effects, related to the electromagnetically induced transparency phenomenon,
are readily observed in experiments, which are found to be in excellent agreement with the theory developed.
Received 28 March 2001 and Received in final form 3 October 2001 相似文献
11.
布里渊光时域分析传感器的消偏振衰落技术 总被引:5,自引:0,他引:5
在布里渊光时域分析(BOTDA)光纤传感器中,由于受激布里渊散射的偏振相关性的影响,激励光和探测光的偏振态随机变化引起的信号起伏严重影响布里渊散射光信号的稳定测量。通过建立与偏振态有关的激励光和探测光的耦合方程,推导出接收探测光光强关于激励光和探测光偏振态的理论公式,并由此提出偏振扩展接收技术。理论分析表明,偏振扩展接收技术可以有效地抑制偏振相关信号衰落。通过对耦合方程进行模拟,验证了理论分析的正确性和偏振扩展接收技术的可行性。最后给出了采用偏振扩展接收的布里渊光时域分析实验结果,与理论分析和模拟具有较好的一致性。 相似文献
12.
The optical parametric oscillator is investigated theoretically for the general case of resonant pump, signal and idler waves. Mean photon numbers, threshold energies and conversion rates are calculated explicitly for different types of the waves (standing and running ones), where in the case of both signal and idler being standing waves the appearance of an oppositely running (“reflected”) pump wave is properly taken into account. In addition, from the equations of motion for the photon creation operators approximately valid rate equations are deduced which in certain cases predict a damped oscillating transition (analogous to the relaxation oscillations of a ruby laser) to the stationary state. 相似文献
13.
The gain recoveries in quantum dot semiconductor optical amplifiers (QD SOAs) are numerically studied by rate equation simulation.
Similar to the optical pump-probe experiment, the injection of double 150 fs optical pulses is used to simulate the gain recovery
of a weak continuous signal under different injection levels, inhomogeneous broadenings, detuning wavelengths, and pulse signal
energies for the QD SOAs. The obtained gain recoveries are then fitted by a response function with multiple exponential terms
to determine the response times. The gain recovery can be described by three exponential terms with the time constants, which
can be explained as carrier relaxation from the excited state to the ground state, carrier captured by the excited state from
the wetting layer, and the supply of the wetting layer carriers. The fitted lifetimes decrease with the increase of the injection
currents under gain unsaturation, slightly decrease with the decrease of inhomogeneous broadening of QDs, and increase with
the increase of detuning wavelength between continuous signal and pulse signal and the increase of the pulse energy. 相似文献
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15.
Zanon T Guerandel S de Clercq E Holleville D Dimarcq N Clairon A 《Physical review letters》2005,94(19):193002
We report the observation of Raman-Ramsey fringes using a double lambda scheme creating coherent population trapping in an atomic ensemble combined with pulsed optical radiations. The observation was made in a Cs vapor mixed with N2 buffer gas in a closed cell. The double lambda scheme is created with lin perpendicular lin polarized laser beams leading to higher contrast than the usual simple lambda scheme. The pulsed trapping technique leads to narrow fringe widths scaling as 1/(2T) with high contrasts which are no longer limited by the saturation effect. This technique operates in a different way from the classical Ramsey sequence: the signal is done by applying a long trapping pulse to prepare the atomic state superposition, and fringe detection is accomplished by optical transmission during a short second trapping pulse without any perturbation of the dark state. 相似文献
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本文由半经典理论推得了原子电离率随脉冲空间传输出现周期性起伏这一新的相干作用结果,这点与速率方程的预计相差甚远.文中定量说明了利用速率方程对同位素分离过程进行分析时产生的系统误差,为实验分析工作提供了依据. 相似文献
18.
In quantum optics, some models are considered to
describe many aspects of the dynamics of atoms coupled to an
electromagnetic field (laser). The simplest atomic model is of
course the two-level-atom which is governed by the Bloch optical
equations. In general this system is solved in the steady state or
by using some approximations. An extended analytic approach is
considered for this coupled equations. The separation approach of
coupled differential equations is always possible with a sequence
of special transformation into nonlinear differential equations.
The conditions that permit an exact solution of three coupled
systems are extracted in a natural manner. The case of sodium atom
moving along the axis of a standing-wave is investigated in some
details. 相似文献
19.
We have developed an analytic treatment of light emission properties of electric and magnetic multipoles near a planar dielectric surface, using angular spectrum representation of vector spherical waves. The results are described in terms of spatial rotation matrix elements, so that the angular distribution of light emission for higher order multipoles is easily obtained, which enables us to evaluate basic optical near-field problems such as electric dipole radiation with arbitrary orientation with respect both to surface and observation direction. The numerical results are in good agreement with our previous experimental results and the numerical results reported by Lukosz. 相似文献
20.
We demonstrate the controlled coherent transport and splitting of atomic wave packets in spin-dependent optical lattice potentials. Such experiments open intriguing possibilities for quantum state engineering of many body states. After first preparing localized atomic wave functions in an optical lattice through a Mott insulating phase, we place each atom in a superposition of two internal spin states. Then state selective optical potentials are used to split the wave function of a single atom and transport the corresponding wave packets in two opposite directions. Coherence between the wave packets of an atom delocalized over up to seven lattice sites is demonstrated. 相似文献