The development of wave optics for light brought many new insights into our understanding of physics, driven by fundamental experiments like the ones by Young, Fizeau, Michelson-Morley and others. Quantum mechanics, and especially the de Broglie’s postulate relating the momentum p of a particle to the wave vector k of an matter wave: k = 2 λ = p/ℏ, suggested that wave optical experiments should be also possible with massive particles (see table 1), and over the last 40 years electron and neutron interferometers have demonstrated many fundamental aspects of quantum mechanics [1].

/pdf/optics-and-interferometry-with-atoms-and-molecules-1vnuwajb51.pdf

Optics and interferometry with atoms and molecules

This paper reviews the basic theory of the mechanical action of light in resonant interaction with atoms. At present the main application is laser cooling, but the approach is applicable to a broader range of phenomena. It is based on an adiabatic elimination philosophy, which turns out to give the lowest-order quantum corrections to the behavior found when the photon momentum goes to zero. Hence it is called a semiclassical theory. In this manner a subjective but consistent approach can be presented; other treatments are incorporated or mentioned at the appropriate places. Both the classical and the quantum-mechanical approach are discussed. Those readers who wish to obtain only a heuristic overview of the phenomena can concentrate on Sec. III, which treats both the photon momentum effects and their connection with photon counting statistics. The detailed theoretical treatment utilizes Wigner functions and Fokker-Planck techniques. The ensuing theory is applied both to the cooling of free particles and trapped ones. The paper ends with an extensive bibliography, where the author lists most papers of interest for research into the mechanical manifestations of light. For completeness, many papers are included that are not explicitly mentioned in the text.

The semiclassical theory of laser cooling

A variety of powerful techniques to control the position and velocity of neutral particles has been developed. As examples of this new ability, lasers have been used to construct a variety of traps, to cool atoms to temperatures below 3 x 10(-6) kelvin, and to create atomic fountains that may give us a hundredfold increase in the accuracy of atomic clocks. Bacteria can be held with laser traps while they are being viewed in an optical microscope, and organelles within a cell can be manipulated without puncturing the cell wall. Single molecules of DNA can now be stretched out and pinned down in a water solution with optical traps. These new capabilities may soon be applied to a wide variety of scientific questions as diverse as precision measurements of fundamental symmetries in physics and the study of biochemistry on a single molecule basis.

https://science.sciencemag.org/content/sci/253/5022/861.full.pdf

Laser manipulation of atoms and particles

Recent progress and future prospects of matter-wave interferometry with complex organic molecules and inorganic clusters are reviewed Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered The theoretical concepts underlying these experiments and the experimental challenges are discussed This includes optimizing interferometer designs as well as understanding the role of decoherence The high sensitivity of matter-wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles The prospects for probing the quantum superposition principle are investigated in the limit of high particle mass and complexity

/pdf/colloquium-quantum-interference-of-clusters-and-molecules-4v5rvstlwh.pdf

Colloquium: Quantum interference of clusters and molecules

Preliminary experimental results are reported for the deflection of Na atoms in an atomic beam by a transverse standing-wave laser field whose frequency is tuned between the two ground-state hyperfine components of the ${D}_{2}$ line In contrast to the two experiments done previously, a splitting of the beam into two symmetric peaks whose separation increases with the electric-field is seen here In addition, the data show evidence for atomic diffraction: a tendency for scattered atoms to acquire momentum in multiples of $2\ensuremath{\hbar}k$

Diffraction of an Atomic Beam by Standing-Wave Radiation

We present a thorough spectroscopic study of the van der Waals molecule NaNe. Our molecular beam apparatus, laser scanning system, and frequency reference technique are described in detail. Methods of rotational analysis are discussed. Descriptions of the observed vibration–rotation bands in the A 2Πr–X 2Σ+ and B 2Σ+–X 2Σ+ manifolds are presented. Perturbations in the observed spectra are discussed. Long range analysis techniques are used to determine the vibrational quantum numbering from observed isotopic shifts and to determine excited and ground state potential parameters. We find DeA=145±05 cm−1 at ReA=5.1(1)a0, DeX=8.1(9) cm−1 at ReX=10.0(1)a0, and DeB?3.0(5) cm−1 at ReB?14.4(3)a0.

Laser spectroscopy of the diatomic van der Waals molecule NaNe

We have observed momentum transfer from a standing-wave light field to an atomic beam. The atomic beam is split symmetrically into two peaks whose separation increases with field strength. The short interaction time ensures that this deflection is due to induced forces; these are described using a semiclassical dressed-atom treatment, which gives good agreement with the data. In addition to the splitting, we have observed diffraction of the atomic beam due to the exchange of even numbers of photons with the field.

Deflection of atoms by standing-wave radiation

This laser induced fluorescence study of NaAr reports the direct observation of vibrational and rotational structure of the B2∑+ state through spectroscopic means of Reference 1. Crossed laser and supersonic molecular beam technique is used. We study highly excited vibrational levels at both A2∏r and B2∑+ states. Several types of rotation induced perturbations are encountered and analyzed. Preliminary intensity calculations for the B‐X system lead us to believe that the adiabatic B2∑+ well minimum must be at smaller internuclear distance than has been estimated before. We estimate that 5.5 A < RBe < 6 A and that the B2∑+ state is at least 30 cm−1 deep. This is in agreement with the latest high resolution scattering data2.

Philip E. Moskowitz

Papers

Diffraction of an Atomic Beam by Standing-Wave Radiation

Laser spectroscopy of the diatomic van der Waals molecule NaNe

Deflection of atoms by standing-wave radiation

High resolution laser induced fluorescence spectroscopy of highly excited vibrational levels in NaAr: A2∏r and B2∑+