Selective reflection spectroscopy at an interface with a low-density resonant vapor, especially when combined with a frequency modulation technique, is a high-resolution Doppler-free tool for probing atoms interacting with a surface. We analyze different types of relevant surface interaction, emphasizing the spectral consequences of a van der Waals surface attraction associated to a
z−3 potential dependence (
z: distance to the wall). We present detailed results of two series of experiments at a Cs vapor/dielectric window interface on the 6S
1/2-6P
3/2 (
λ=852 nm) resonance line and on the 6S
1/2-7P second resonance line (
λ=455 nm and 459 nm). Lineshape analysis at various pressures consistently shows that a van der Waals-type surface attraction has to be considered to interpret strong lineshape distortions and resonance shift. The attractive strengths are found to be equal respectively to
≈2 kHz
μm
3 and
≈20 kHz
μm
3, independently of the considered hyperfine component, within the experimental accuracy. It yields also typical parameters of pressure broadening and shift, which are shown to originate in collisional processes, at densities where the medium is opaque. Theoretical expectations for the VW strength are discussed on the basis of the results of atomic theory. The predicted values are smaller, by a typical factor of 2, than those deduced from the experiments. The validity of the theory, when applied to a dielectric interface, is discussed and seems questionable when the frequency of virtual atomic transitions involved in the van der Waals attraction potential lies in the dielectric window absorption range.
Frequency-modulated selective-reflection spectroscopy of the 6S-7P Cs resonance line yields Doppler-free anomalous line shapes that we demonstrate to be fully dominated by the long-range atom-surface interaction potential. The spatial inhomogeneous broadening of the observed line shapes, as well as its dependence on the pressure, the nature of the dielectric window, and the light incidence angle, is fully interpreted with a z(-3) van der Waals attraction model. These experiments clearly prove the feasibility of a spectral analysis of atom-surface interactions.
The atomic response to resonant light irradiation near vapor-dielectric interfaces is monitored via high-resolution reflection spectroscopy. One demonstrates that this Doppler-free spectroscopic technique yields a novel probe of atomic dynamics and QED atom-surface long- range interaction. It provides for the first time a spectral evidence of van der Waals attraction, and the method is intrinsically applicable to the observation of surface interaction exerted on excited atoms. Effects related with atomic excitation level, nature of the dielectrics, and atomic collisions are discussed.
This reports on the surface attraction exerted onto Cs(8P), as measured through the selective reflection spectroscopy (SR) technique via a one- photon excitation at 388 nm from the ground state. In a series of experiments on the Cs (6S/sub 1/2/-8P/sub 3/2/) transition in front of a sapphire surface, the accuracy in the van der Waals evaluation, and with an improved fitting method, should be on the order of 10%. Further developments, expected to be reported too, concern the fine structure component Cs (6S/sub 1/2/-8P/sub 3/2/) , along with a study of SR spectroscopy at various interfaces.