X rays from quasimolecules

Abstract

In slow heavy-ion-atom collisions, inner-shell electrons with velocities larger than the projectile velocity form diatomic molecular orbitals around the projectile and target nuclei. If a vacancy exists in one of these orbitals, it can decay at some point during collision, emitting an x ray characteristic of the molecular transition energy at that internuclear distance. Since the projectile-target internuclear distance varies during the collision, x-ray continua are seen, which for \so molecular-orbital x rays (transitions to vacancies in the lowest Iscr orbital) stretch toward the united-atom AT-shell binding energy. This paper reviews the theory of and the experimental evidence for molecular-orbital x-ray emission. A historical overview of the development of these studies is given, showing how the theory of quasimolecular x-ray emission has evolved from a semiclassical quasistatic model to a general dynamic theory, including the Coriolis coupling between molecular orbitals making up the initial and final states. X-ray cross section, angular distribution, and other measurements are discussed, and their impact on the development of the theory of molecularorbital x-ray emission is illustrated.

X‐Rays from Accelerated Ion Interactions

“…Energetic ions produce continuum X-ray emission via both inverse bremsstrahlung (Boldt and Serlemitsos 1969, hereafter IB) and bremsstrahlung from secondary knock-on electrons (see also Anholt 1985). For nonrelativistic protons interacting in stationary H, the inverse bremsstrahlung cross section is identical to the bremsstrahlung cross section for electrons of kinetic energy (m e /m p )E also interacting in stationary H; here m e and m p are the electron and proton masses respectively and E is the proton kinetic energy.…”

Optical Transitions and Charge-Exchange in Highly Charged Quasi-Molecules

“…Transition Moments for the Molecule Z 1 eZ 2 This part is devoted to the calculation of the energy terms and the dipole transition matrix elements and related optical values, for multicharged one electron diatomic quasi-molecules with unequal nuclear charges Z 1 and Z 2 (Z 1 eZ 2 notation for the quasi-molecule). The first wave of interest for such molecules was initiated by spectroscopic observations attributed to inner-shell excitations in ionatom collisions [17,18]. Another wave came from the hot dense plasma physics community.…”

“…The formula (17) gives an analytical description in four different regions of the spectral profile: a Lorentzian region situated near the center Δω ≈ 0, a blue wing with one Condon point, an antistatic region of classically forbidden transitions with no Condon point, and a region corresponding to transitions near the extrema of the potential-difference curve. Figure 6 gives the example of the Lyα profile produced in F +8 − F +9 collisions.…”

Search for interference structures in the quasimolecular X-ray-andK-vacancy production in close collisions of 462 MeV hydrogen-like Kr ions on Mo solid targets

“…Information from inner shells of quasimolecular systems was obtained by studying of MO (molecular orbital) X-ray production [1] and by investigations of K-vacancy creation in the projectile and the target system. Quasimolecular states can be formed during near-symmetric ion-atom collisions at impact velocities smaller than the Bohr-electron velocities of the participaring collision partners.…”