Context. Astronomical spectra of hot molecular clouds in the wavelength range from centimeter to submillimeter show a huge number of rotational lines due to the emission of complex organic molecules, and a large fraction of these lines are unidentified. The assignment of these unidentified lines to new molecules, to known molecules in excited states, or to their isotopologues requires a good knowledge of the spectroscopic parameters of these molecules. Aims. We present the experimental study of the spectroscopic properties of 13 C-substituted ethyl cyanide 13 CH 3 CH 2 CN, CH 3 13 CH 2 CN, and CH 3 CH 2 13 CN. Methods. The rotational spectra of the three species in the ground state have been measured in the frequency ranges from 5 to 26 GHz using waveguide Fourier transform spectrometers and from 160 to 360 GHz using a source-modulated spectrometer employing backward-wave oscillators (BWOs). Results. A new accurate set of spectroscopic constants has been determined for each isotopic species. This permits prediction of the position of rotational lines that are best suited for detection with an accuracy of a few hundreds of kHz. The three isotopologues have been detected in an Orion IRc2 IRAM survey via several hundred of lines, illustrating that many "unidentified" bands are definitely due to isotopologues of known molecules.

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Recent demonstrations of both heat-to-electricity energy conversion devices and electrocaloric devices based on first-order ferroelectric phase transformations identify the lowering of hysteresis and cyclic reversibility of the transformation as enabling criteria for the advancement of this technology. These demonstrations, and recent studies of the hysteresis of phase transformations in oxides, show that satisfying conditions of supercompatibility can be useful for lowering hysteresis, but with limitations for systems with only a few variants of the lower symmetry phase. in particular, it is widely accepted that in a classic cubic-to-tetragonal phase transformation, with only three tetragonal variants having only six twin systems, tuning for improved crystallographic compatibility will be of limited value. This work shows that, on the contrary, the tuning of lattice parameters in Ba(Ti 1-x Zr x)o 3 for improved crystallographic compatibility, even at low doping levels of Zr (x ≤ 0.027), give significant improvement of transformation and ferroelectric energy conversion properties. Specifically, the transformation hysteresis is lowered by 25%, and the maximum value of the polarization/temperature ratio dP/dT at the phase transformation is increased by 10%. Recently, new devices for the direct (i.e. without a separate electrical generator) conversion of heat to electricity have emerged based on first order ferroelectric phase transformations 1,2. These devices are designed to harvest energy from small temperature differences in the environment, from industrial sources, or from computers and digital devices. From a materials science perspective the main challenges facing the development of this technology, as identified in these papers, are the management of leakage, the cyclic reversibility of the transformation, and the minimization of hysteresis. The latter, which is of interest here, is identified as the main source of loss in this application. In metals, most prominently in TiNi-based shape memory alloys, an understanding of the factors affecting reversibility and hysteresis is quite far advanced. For a high cyclic reversibility it is well-accepted 3 that having a high to low symmetry transformation with a group-subgroup relation, small volume change, and the existence of many low energy austenite/martensite interfaces are desirable. As an example of the influence of these factors, no reasonable shape memory effect has been demonstrated using any metal with a cubic-to-tetragonal phase transformation in polycrystalline form. As demonstrated in slightly Ni-rich TiNi alloys, a fine array of suitable coherent precipitates is also highly desirable, as is a fine, but not too fine, grain size 3,4. The most dramatic improvements in cyclic reversibility, and also thermal hysteresis, have been achieved by tuning the lattice parameters to satisfy conditions of supercompatibility 5-8. Supercompatibility refers to special conditions on the lattice parameters that eliminate stressed transition layers between phases. The simp...

The ability to reproducibly synthesize thin films with precise composition and controlled structure is essential for fundamental study and mass production. Here, we demonstrate the hybrid molecular beam epitaxy (MBE) growth of epitaxial, single crystalline BaTiO3 films with different thicknesses on Nb-doped SrTiO3 substrates with atomically smooth surfaces. By combining scanning transmission electron microscopy, temperature-dependent high-resolution x-ray diffraction, reflection high-energy electron diffraction, and atomic force microscopy, we study the effect of growth conditions and the interplay between stoichiometry and epitaxial strain on the resulting structure. Furthermore, we demonstrate a close to bulk-like ferroelectric phase transition in thicker films and highlight the effect of strain on the phase transition temperature. This work establishes the hybrid MBE approach for the growth of heteroepitaxial BaTiO3 films on conducting substrates with scalable thickness and controlled stoichiometry.