Atoms in External Fields

Abstract

Sections 8.1–8.4 present the essentials on these topics. The reader should become well acquainted with these key tools in modern atomic physics – even though parts of it may seem somewhat strenuous at first sight. These concepts are essential also for molecular physics, as well as for a fundamental understanding of many properties of condensed matter and plasmas. This will be illustrated in Sects. 8.1.6, 8.1.7, 8.1.8, 8.2.10, 8.3 and 8.4.2 for a number of selected examples. In these presentations the reader will also find various references to modern developments in atomic physics which will brighten the study of these “classical” themes with currently hot topics – as e.g. “fast and slow” light in Sect. 8.4.4 or, in Sect. 8.5, with a first approach towards the rapidly developing modern research field of matter in intense and ultra-intense laser fields.

The interaction of atoms with external magnetic fields ( Zeeman effect) has already been introduced in Chaps.  1 and  2 , while radiation induced transitions where treated in Chaps.  4 and 5 . Here we generalize and deepen what is already known, and develop the tools for a quantitative description of atoms and molecules in external magnetic and electric fields. Thus, this chapter provides the essential basis for understanding this type of interaction also in a more complex environment and gives first examples of how to approach macroscopic properties of matter, such as magnetism and dielectric polarization.

Acronyms and Terminology

ADK:

‘Ammosov, Delone, and Krainov’, (1986) theory for strong field ionization (see e.g. Sect. 8.30).

AMO:

‘Atomic, molecular and optical’, physics.

ATI:

‘Above-threshold ionization’, in multi-photon ionization, if more photons are absorbed than necessary for ionization.

a.u.:

‘atomic units’, see Sect. 2.6.2.

DC:

‘Direct current’, unidirectional electric voltage and current.

E1:

‘Electric dipole’, transitions induced by the interaction of an electric dipole with the electric field component of electromagnetic radiation.

EPR:

‘Electron paramagnetic resonance’, spectroscopy, also called electron spin resonance ESR (see Sect. 9.5.2).

esu:

‘electrostatic units’, old system of unities, equivalent to the Gauss system for electric quantities (see Appendix A.3).

FS:

‘Fine structure’, splitting of atomic and molecular energy levels due to spin orbit interaction and other relativistic effects (Chap. 6).

good quantum number:

‘Quantum number for eigenvalues of such observables that may be measured simultaneously with the Hamilton operator (see Sect. 2.6.5)’.

HHG:

‘High harmonic generation’, in intense laser fields.

HV:

‘High voltage’, electric voltages typically higher than $1000\operatorname{V}$.

IR:

‘Infrared’, spectral range of electromagnetic radiation. Wavelengths between $760\operatorname{nm}$ and $1\operatorname{mm}$ according to ISO 21348 (2007).

LHC:

‘Left hand circularly’, polarized light, also σ ⁺ light.

MPI:

‘Multi-photon ionization’, ionization of atoms or molecules by simultaneous absorption of several photons.

NIST:

‘National institute of standards and technology’, located at Gaithersburg (MD) and Boulder (CO), USA. http://www.nist.gov/index.html.

NMR:

‘Nuclear magnetic resonance’, spectroscopy, a rather universal spectroscopic method for identifying molecules (see Sect. 9.5.3).

QED:

‘Quantum electrodynamics’, combines quantum theory with classical electrodynamics and special relativity. It gives a complete description of light-matter interaction.

RHC:

‘Right hand circularly’, polarized light, also σ ⁻ light.

SI:

‘Système international d’unités’, international system of units (m, kg, s, A, K, mol, cd), for details see the website of the Bureau International des Poids et Mésure http://www.bipm.org/en/si/ or NIST http://physics.nist.gov/cuu/Units/index.html.

SVE:

‘Slowly varying envelope’, approximation for electromagnetic waves (see Sect. 1.2.1, specifically Eq. (1.38), Vol. 2).

Ti:Sapph:

‘Titanium-sapphire laser’, the ‘workhorse’ of ultra fast laser science.

UV:

‘Ultraviolet’, spectral range of electromagnetic radiation. Wavelengths between $100\operatorname{nm}$ and $400\operatorname{nm}$ according to ISO 21348 (2007).

VIS:

‘Visible’, spectral range of electromagnetic radiation. Wavelengths between $380\operatorname{nm}$ and $760\operatorname{nm}$ according to ISO 21348 (2007).

VUV:

‘Vacuum ultraviolet’, spectral range of electromagnetic radiation. part of the UV spectral range. Wavelengths between $10\operatorname{nm}$ and $200\operatorname{nm}$ according to ISO 21348 (2007).

XUV:

‘Soft X-ray (sometimes also extreme UV)’, spectral wavelength range between $0.1\operatorname{nm}$ and $10\operatorname{nm}$ according to ISO 21348 (2007), sometimes up to $40\operatorname{nm}$.