We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a p-wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral line shape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, n. Spectral features are described with a functional determinant approach (FDA) that solves an extended Fröhlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with a FDA.

We present a quantum many-body description of the excitation spectrum of Rydberg polarons in a Bose gas. The many-body Hamiltonian is solved with a functional determinant approach, and we extend this technique to describe Rydberg polarons of finite mass. Mean-field and classical descriptions of the spectrum are derived as approximations of the many-body theory. The various approaches are applied to experimental observations of polarons created by excitation of Rydberg atoms in a strontium Bose-Einstein condensate.

A biodegradable polymer composite containing lignin from sugarcane bagasse and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was produced and characterized in terms of its thermal, morphological, and mechanical properties. For comparison with the properties of the composites, the properties of the isolated composite components (lignin and PHBV) were also determined. The characterizations were carried out by Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and mechanical properties. In the micrograph images, no physical contact between filler and matrix was verified. The thermal decomposition profiles of composites depend on the lignin/PHBV proportions, and their residual mass increased as a function of lignin amount. Higher temperatures were necessary to promote PHBV crystallization in the presence of lignin. However, the crystalline degree of composites was not affected by the lignin. The results obtained in the mechanical tests showed that the lignin addition caused a decrease of mechanical properties.

The lifetimes of the lower-lying vibrational states of ultralong-range strontium Rydberg molecules comprising one ground-state 5s2 1S0 atom and one Rydberg atom in the 5s38s 3S1 state are reported. The molecules are created in an ultracold gas held in an optical dipole trap and their numbers determined using field ionization, the product electrons being detected by a microchannel plate. The measurements show that, in marked contrast to earlier measurements involving rubidium Rydberg molecules, the lifetimes of the low-lying molecular vibrational states are very similar to those of the parent Rydberg atoms. This results because the strong p-wave resonance in low-energy electronrubidium scattering, which plays an important role in determining the molecular lifetimes, is not present for strontium. The absence of this resonance offers advantages for experiments involving strontium Rydberg atoms as impurities in quantum gases and for testing theories of molecular formation and decay

Amino acids of propolis samples from different origins were analysed and quantified. Seven of them presented almost the same percentage in all samples, indicating that bees may have obtained amino acids from three sources: plants, pollen contamination and from their own metabolism. The regeneration properties of propolis in relation to the presence of some amino acids are discussed.