1. In this presentation we investigate the polarization bremsstrahlung (PB) on multi-atomic targets. PB appears due to projectile-target interaction that polarizes both the target’s electron shell and that of a projectile inducing in it a time-dependent dipole moment that radiates. PB may be more intensive than ordinary bremsstrahlung (OB) of a charge [1].

2. In case of a multi-atomic target the projectile simultaneously polarizes several atoms and one should expect prominent alteration of the emission spectrum due to interference effects. As a projectile, we chose an incoming atom, for which PB absolutely dominates over OB. As a target a regular linear chain of fullerenes is chosen and OB is considered similarly to radiation in the ion – atom’s chain collisions [2].

3. We derive the PB spectrum without and will taking into account both the polarization of the target fullerenes and the incoming atom. We demonstrate its prominent alteration as compared to that of OB. We limit ourselves to elastic PB only, in which all energy lost by projectile is emitted as a single photon.

4. For non-relativistic projectiles the differential cross-section of emitting a single photon neglecting the polarization of the projectile can be presented as follows

       (1)

Here  is the photon energy, is the photon emission solid angle, c is the speed of light, v is the projectile’s velocity, Z_p and N_p are the projectile’s nuclear charge and number electrons in it,  is the dipole polarizability of a single fullerene, R_p is the projectile radius,  is the photon momentum direction, N is the total number of fullerenes in the chain and d is the inter-fullerene distance. We use atomic units.

6. If one takes into account the projectile possible polarization, one has instead of (1) the following relation

(2)

Here the lower index p (f) marks corresponding characteristics for projectile (target).

7. The differential cross-section in (1) and (2) differs from that for a collision of an incoming atom and fullerene by the factor  that is quite big if , while . In this case the enhencement factor  is big and independent upon N. If the target chain of fullerenes is not too long, one can have  that leads to .

8. We have demonstrated that interference effects in PB generation on an atomic chain are strong. They lead to growth of the intensity of radiation and with increase of projectile speed lead to its preferential orientation along the chain’s axis. Of interest is to consider motion of two chains, that of atoms and fullerenes along each other as well as the case of an atom moving above a system of fullerenes chains forming a flat surface, or above a sheet of graphene.

References

[1] M Ya Amusia 2006 Rad. Phys. Chem. 75 1232.

[2] M Ya Amusia and V I Matveev 2013 JETP Letters 97 379