Laser-induced excitation of electronic rydberg wave packets

We give a qualitative review of theoretical ideas and experimental work on laser-induced excitation of atomic Rydberg wave packets. Studying the motion of Rydberg wave packets with the help of short or intense laser pulses provides a bridge between quantum mechanics and the classical concept of the trajectory of an electron and corresponds to the real-time observation of atomic dynamics.     

Laser-induced optical activity in range of Rydberg autoionizing states of xenon

Optical activity of xenon atoms in the vacuum UV range induced by circularly polarized laser light is studied theoretically. The optical activity arises in the vicinity of the autoionizing state 5p ⁵(² P _1/2)8s′$ \left[ {\frac{1} {2}} \right]_1 $ \left[ {\frac{1} {2}} \right]_1 as a result of its coupling via the laser field with the discrete state 5p ⁵(² P _3/2)7p $ \left[ {\frac{1} {2}} \right]_1 $ \left[ {\frac{1} {2}} \right]_1 . Polarization variations of the vacuum UV radiation upon its propagation through the atomic medium are calculated, and the possibility of controlling this polarization is discussed. Manifestations of nonresonant coupling of the discrete state with the broad autoionizing state 5p ⁵(² P _1/2)6d′$ \left[ {\frac{1} {2}} \right]_1 $ \left[ {\frac{1} {2}} \right]_1 induced by the overlap of the Rydberg autoionizing series in xenon are studied.     

Laser-induced fluorescence of metastable xenon ions

Xenon ions in the metastable state 5d ⁴D_{$\text{7}\text{2}$} are excited by means of a tunable dye laser at 6051 Å. The excitation is monitored by non-resonant fluorescence at 5292 Å.     

Vibrational autoionization in rydberg states of ammonia

Rotationally resolved photoelectron spectroscopy is used to elucidate the mechanism for vibrational autoionization via the nontotally symmetric umbrella vibration of ammonia ( NH3). This mechanism depends strongly on the character of the autoionizing level, and the data demonstrate that both the electronic and rotational degrees of freedom can compensate for the change in vibrational symmetry that occurs for odd changes in the quantum number of the umbrella vibration. This result has implications for models of the mode dependence of vibrational autoionization in polyatomic molecules.     

High resolution spectroscopy of rydberg states in indium I

Two-photon laser spectroscopy in a dense indium vapour allowed to investigatenp ² P _{1/2, 3/2} states (n=27–35) for^{113, 115}In with a thermionic diode. Precise data on the fine structure splitting of these states and the isotope shift of the two photon transitions have been obtained. The fine structure splitting shows a hydrogenic behaviour. By using the result of our isotope shift measurement in combination with literature values, level isotope shifts with reference to the ionization limit are deduced and analysed with respect to the different contributions.     

Laser-induced fluorescence study of a xenon Hall thruster

2 ⁰→6p[3/2]₂(³P₂-¹D₂) transition at 823.2 nm and the xenon-ion 5d[3]_7/2→6p[2]_5/2 ⁰(⁴D_7/2-⁴P_5/2) transition is used to measure plasma parameters in the plume of a laboratory-model xenon Hall thruster. The Hall discharge operates nominally at 62 V, 4.2 A, and 3.2 mg s^-1 xenon flow, with an overall thruster power of 320 W. A tunable semiconductor diode laser and an Ar⁺-pumped dye laser are used to probe the respective excited-state transitions. Axial velocity measurements are made at a number of axial and radial locations up to 4.5 cm downstream of the thruster-exit plane and under a variety of thruster operating conditions. Neutral velocities from 100 m s^-1 to 400 m s^-1 and ion velocities as high as 12 km s^-1 are calculated from measured Doppler shifts. The charge-exchange phenomenon evidently does not significantly affect the xenon neutrals. The spectral-line shapes of the ion indicate a spread in ion energies through a non-Maxwellian distribution of axial velocities. Neutral kinetic temperatures of 500 (±200) K are observed under standard operating conditions. Zeeman and Stark effects on the spectral-line shapes, from the thruster’s magnetic and electric fields, are not substantial. The measured line center of the ion transition is 16521.23 (±0.02) cm^-1. Received: 20 January 1997/Revised version: 12 May 1997     

Capture into rydberg states and momentum distributions of ionized electrons

The yield of neutral excited atoms and low-energy photoelectrons generated by the electron dynamics in the combined Coulomb and laser field after tunneling is investigated. We present results of Monte-Carlo simulations built on the two-step semiclassical model, as well as analytic estimates and scaling relations for the population trapping into the Rydberg states. It is shown that mainly those electrons are captured into bound states of the neutral atom that due to their initial conditions (i) have moderate drift momentum imparted by the laser field and (ii) avoid strong interaction (“hard” collision) with the ion. In addition, it is demonstrated that the channel of capture, when accounted for in semiclassical calculations, has a pronounced effect on the momentum distribution of electrons with small positive energy. For the parameters that we investigated its presence leads to a dip at zero momentum in the longitudinal momentum distribution of the ionized electrons.     

Low-spin states of odd-mass xenon isotopes

In this work, we analyse the positive parity of states of odd-mass nucleus within the framework of interacting boson-fermion model. The result of an IBFM-1 multilevel calculation with the 2d_5/2, 1g_7/2, 3s_1/2, 2d_3/2 and 1h_11/2, single particle orbits is reported for the positive parity states of the odd-mass nucleus ^125–129Xe. Also, an IBM-1 calculation is presented for the low-lying states in the even-even ^124–128Xe core nucleus. The energy levels and B(E2) transition probabilities were calculated and compared with the experimental data. It was found that the calculated positive parity low-spin state energy spectra of the odd-mass ^125–129Xe isotopes agree quite well with the experimental data.      

Inert gases’ collisional broadening and shift of thallium rydberg states

Summary The broadening and shift of thallium 6P _1/2–10P _1/2,3/2 transitions perturbed by argon and helium gas have been measured by two-photon Doppler-free absorption and ionization detection. Broadening and shift coefficients for He+Tl and Ar+Tl are obtained and van der Waal constants are determined.

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Riassunto L’allargemento e lo spostamento delle transizioni 6P _1/2–10P _1/2,3/2 del tallio disturbate dai gas argon ed elio sono statimisurrrati da un’osservazione di assorbimento e ionizzazione in assenza di effetto Doppler a due fotoni. Si ottengono i coefficienti di allargamento e spostamento per He+Tl e Ar+Tl e si determinano le costanti di van der Waals.

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Резюме Измеряются уширение и сдвиг 6P _1/2–10P _1/2,3/2 переходов в таллии, возмущенном аргоном и гелием. Получаются козффициенть уширения и сдвита для He+Tl и Ar+Tl. Определяются постояннйе ван дер Ваальса.

     

Evidence for high-l rydberg states in atomic lithium excited by electron impact

By a time-of-flight technique we have studied the radiative decay of lithium atoms excited to high Rydberg levels by electron impact. The observed decay rates are consistent with large values for the orbital angular momentum quantum number l.     

Laser-induced transitions between triply excited hollow states

We present an ab initio calculation of the Li+ photoion yield in the presence of laser coupling between the triply excited 2s(2)2p(2)P(o) and 2s2p(2) (2)D(e) resonances in lithium, the first of which is assumed excited by synchrotron radiation from the ground state. The laser coupling between the triply excited states is shown to lead to a significant and readily measurable modification of the line profile which provides a unique probe of the dipole strength between highly correlated triply excited states.     

Radiative lifetimes of some excited states of neutral xenon

The radiative lifetimes of ten levels belonging to the nf (n=4-7) and three levels belonging to the ns (n=8,9) configuration of XeI have been measured using the high frequency deflection technique together with a delayed coincidence single-photon counting arrangement. Lifetimes of some of the levels have been measured for the first time. The results have been compared with other experimental and theoretical values.     

铍原子里德堡能级的计算(英文)

依据最弱受约束电子势模型理论,计算了铍原子1s~22sns~1S_0(n=3～50)、1s~22snp~1P_1~0(n=3～50)_和1s~22snd~1D_2(n=3～50)里德堡系列能级和量子亏损.计算结果与已有的实验结果符合得很好.     

Laser spectroscopy of the rydberg states of atoms group IIB (Zn, Cd, Hg)

An investigation has been made of the³P_0,1,2-series of Zn (n=17–60), Cd (17–50), and Hg (18–60) atoms by the method of laser three-step photoionization. The energy (E_n) values and quantum defects (Δ) of these states are determined. The ionization potentials of the atoms are refined by matching the convergence of the Rydberg series. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 249–250, March–April, 2000.     

Correlation of electronic states of the positive ions of xenon tetrafluoride,xenon oxide tetrafluoride,and iodine pentafluoride

A correlation of electronic states of XeF₄⁺, XeOF₄⁺ and IF₅⁺ is presented. The results are interpreted in terms of the molecular orbitals of the neutral molecules via Koopmans' Theorem. The results strongly suggest that the first band in the ultraviolet photoelectron spectrum of XeOF₄ contains only two electronic states. Consequently, the Xe-O σ bond in XeOF₄ is at least 1.5 eV more stable than the corresponding xenon lone pair in XeF₄. The interpretation of oxygen lone pair electron energies is complicated by ionic and covalent effects, both tending to stabilize these electrons.