Surface scattering of atoms for high-sensitivity spectroscopy

High-sensitivity laser spectroscopy is integral to applications such as atomic clocks, quantum computers, and chemical sensing. Doppler broadening is the main factor limiting its resolution and is typically reduced by collimation with an aperture. Hower, collimation causes the atom beam to suffer a considerable loss of flux. Another way to mitigate Doppler broadening is via beam temperature, which is typically determined by the oven used to create the atom vapor. Lowering the atomic temperature decreases spectral Doppler broadening and increases the transit time across the excitation laser. However, reducing the oven temperature also reduces the flux. Therefore, a separate method of cooling atoms without much flux loss is needed. We find that a polydimethylsiloxane (PDMS)-coated surface can cool iron atoms from approximately 1400 K to room temperature by surface scattering. It is also apparent that a single scattering event is enough for atoms to equilibrate with the surface temperature of the PDMS. Further, we reveal the very low adsorption of iron and ytterbium atoms on PDMS, an effect that persists at surface temperatures down to 200 K. Through numerical simulations, we demonstrate the potential use of surface scattering in creating a room-temperature source of collimated atoms with enhanced flux and reduced velocity compared to one without surface scattering.