Laser-induced continuum structure in multiphoton ionisation

Dressed-state resonances can be induced in photoionisation continua by radiative coupling from energetically accessible bound states. Such resonances lead to enhanced photoionisation rates and interference minima. We present results on the effects of saturation and Rabi oscillations on ion yields and asymmetries in AC Stark-split photoelectron spectra.     

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.     

Laser-induced effects for overlapping autoinoizing rydberg states of xenon

The effect of a laser field on the cross section of photoionization of an atom by probe radiation in the region of closely lying autoionizing resonances is studied theoretically. The cross sections in the region of the overlapping autoionizing Rydberg states 5p ⁵(² P _1/2)6d′ J = 1 and 5p ⁵(² P _1/2)8s′ J = 1 resonantly coupled with the discrete state 5p ⁵(² P _3/2)7p[1/2]₁ in the xenon atom are calculated. The behavior of the shape and position of resonances in relation to the frequency and intensity of laser radiation is studied.     

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     

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.