Coherence in collisionally excited N = 2 levels of hydrogen

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:5541124

Stone, Jr, J A

We have observed coherence between 2s and 2p states of atomic hydrogen excited in collisions of 2 to 30 keV ground-state hydrogen atoms with He, Ar, H/sub 2/, N/sub 2/, and O/sub 2/. The collisional excitation took place in the presence of an axial electric field directed parallel or antiparallel to the hydrogen beam. Lyman-alpha emission perpendicular to the beam changed by a few percent when the direction of the field was reversed. We interpret this change as indicating that the collision excites a linear superposition of 2s and 2p states (coherent excitation). Results are given for the mixed cross section ..cap alpha../sub spo/, which characterizes the collisional coherence. The real part of ..cap alpha../sub spo/--which is proportional to the dipole moment of the excited atom--varies substantially over the 2 to 30 keV range. For a He target at intermediate energies and an Ar target at low energies, it is comparable in magnitude to the 2s and 2p excitation cross sections. The measurement was much less sensitive to the imaginary part of ..cap alpha../sub spo/; meaningful values for this quantity could be obtained (with large error bars) only for He and Ar targets, over portions of the energy range where the coherence signal was large. The method employed in this experiment should be generally applicable to studies of coherent excitation of opposite-parity states and can provide new tests of scattering calculations.

• Research Organization: Massachusetts Univ., Amherst (USA)
• OSTI ID: 5541124
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ARGON
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
COLLISIONS
CROSS SECTIONS
DATA
ELEMENTS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXPERIMENTAL DATA
FLUIDS
GASES
HELIUM
HYDROGEN
INFORMATION
KEV RANGE
KEV RANGE 10-100
MOLECULE COLLISIONS
NITROGEN
NONMETALS
NUMERICAL DATA
OXYGEN
RARE GASES