Effect of pressure-dependent quantum interference on the ac Stark shifting of two-photon resonances

Journal Article · Wed Sep 01 00:00:00 EDT 1993 · Physical Review A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.48.2334· OSTI ID:6242746

Payne, M G; Zhang, J Y ^[1]; Garrett, W R ^[2]

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1. Department of Physics, Georgia Southern University, Statesboro, Georgia 30460-8031 (United States)
2. Chemical Physics Section, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

We describe ac Stark shift production and measurement in a two-laser mode where a first laser is tuned through a two-photon resonance between the ground state and an excited state in order to record a line shape for the corresponding resonantly enhanced multiphoton ionization. A second laser is tuned to a fixed wavelength which is close to a resonance between the upper state in the two-photon transition and a third state which has dipole-allowed transitions back to the ground state. At low concentrations the second laser leads to very large ac Stark shifts in the two-photon excitation and in the related resonantly enhanced multiphoton ionization. However, at high concentrations a destructive interference occurs involving the three-photon coupling between the third state and the ground state and the one-photon coupling due to the four-wave-mixing field at frequency 2[omega][sub [ital L]1][plus minus][omega][sub [ital L]2]. This interference leads to a pressure-dependent suppression of the amplitude for the third state. When this destructive interference occurs, the ac Stark shift due to the second laser undergoes a corresponding pressure-dependent suppression. The criteria for the pressure to be high enough to completely suppress the ac Stark shift is that the real part of phase mismatch [vert bar][Delta][ital k][vert bar] at the angular frequency 2[omega][sub [ital L]1][plus minus][omega][sub [ital L]2] and (or) the absorption coefficient [beta] at the same frequency should be very large, so that with unfocused focused beams [vert bar][Delta][ital k][vert bar][ital L][gt]5[[Delta][sub [ital s]][sup (max)][tau]][sup 1/2], where [ital L] is the thickness of gas penetrated before the shift is measured, [Delta][sub [ital s]][sup (max)] is the maximum ac Stark shift at very low pressure, and [tau] is the pulse length of the lasers.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6242746
• Journal Information: Physical Review A; (United States), Vol. 48:3; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
XENON
STARK EFFECT
AC SYSTEMS
EXCITATION
EXPERIMENT PLANNING
INHIBITION
INTERFERENCE
IONIZATION
LASERS
MULTI-PHOTON PROCESSES
PHOTON COLLISIONS
RESONANCE
TUNING
COLLISIONS
ELEMENTS
ENERGY SYSTEMS
ENERGY-LEVEL TRANSITIONS
FLUIDS
GASES
NONMETALS
PLANNING
POWER SYSTEMS
RARE GASES
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)