The key to ion beams' polarisability

July 17, 2013

Polarisability determines the force with which an inhomogeneous external electric field acts on the ions of an ion beam. However, it can be quite tricky to obtain accurate values for this force. Now, two German theoretical chemists, Volker Koch from Bielefeld University and Dirk Andrae from the Free University Berlin, have devised formulas providing the polarisability of atomic ions as a function of their total charge number. Their findings, about to be published in EPJ D, have implications for many applications, ranging from the use of ion beams for research purposes or as a source for dopant atoms in semiconductor manufacturing to the modelling of planetary and stellar atmospheres.

Being a characteristic quantity of an atom's or ion's electronic state, the polarisability of or ions with several electrons had been difficult to obtain to date because simple equations for it were not available. Most previous theoretical studies of polarisability focused on individual atoms, or early members of series with a constant number of electrons, so called isoelectronic sequences. The electron numbers were usually small, and closed-form expression for the polarisability was never provided. A single exception to this situation were the formulae related to the so-called Stark effect in hydrogen-like atoms derived by Austrian physicist Erwin Schrödinger and Russian-American physicist Paul Epstein, back in 1926.

In their study, the authors used a numerical method to calculate the energy of atoms and ions of a given isoelectronic sequence under various strengths of an external electric field. This numerical approach makes it possible to derive the polarisability of atoms with small to large electron numbers using conventional techniques of numerical analysis.

Koch and Andrae thus established a rational function for each isoelectronic sequence to represent the polarisability data previously established with the numerical method. In addition to generalising previous findings made on hydrogen-like atoms, this research also provides a reference for future use.

Explore further: Magnetic shielding of ion beam thruster walls

More information: European Physical Journal D 67: 139, DOI 10.1140/epjd/e2013-40191-5

Related Stories

Magnetic shielding of ion beam thruster walls

February 13, 2013

Electric rocket engines known as Hall thrusters, which use a super high-velocity stream of ions to propel a spacecraft in space, have been used successfully onboard many missions for half a century. Erosion of the discharge ...

New method to generate Laughlin states with atomic systems

July 3, 2013

In 1998, the Nobel Prize in Physics was conferred to the discovery of a new type of quantum fluid with fractional charge excitations, known as Laughlin state. The production of this quantum state, which explains the behaviour ...

New methods for ion cooling

November 26, 2012

Among the most important techniques developed in atomic physics over the past few years are methods that enable the storage and cooling of atoms and ions at temperatures just above absolute zero. Scientists from Bangalore ...

Eavesdropping on lithium ions

July 8, 2013

( —Lithium ion batteries are at the energetic heart of almost all things tech, from cell phones to tablets to electric vehicles. That's because they are a proven technology, light, long-lasting and powerful. But ...

Elucidating energy shifts in optical tweezers

May 8, 2013

A small piece of paper sticks to an electrically charged plastic ruler. The principle of this simple classroom physics experiment is applied at the microscopic scale by so-called optical tweezers to get the likes of polystyrene ...

Recommended for you

Solving the riddle of the snow globe

May 25, 2017

If you've shaken a snow globe, you've enjoyed watching its tiny particles slowly sink to the bottom. But do all small objects drift the same way and at the same pace?


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.