摘要：Context. Cysteamine (NH2CH2CH2SH), a molecule of potential astrobiological interest, has not yet been detected in the interstellar medium. Furthermore, the sulfur-substituted isomer of ethanolamine (or 2-aminoethanol) has been recently detected in the molecular cloud G+0.693–0.027. Aims. In order to conduct a new interstellar search for cysteamine in the molecular cloud G+0.693–0.027, its pure rotational spectrum needs to be investigated in the laboratory. Methods. A pulsed-jet Fourier transform microwave spectrometer and a Stark-modulated free-jet millimeter-wave absorption spectrometer were used to measure the purely rotational spectrum of cysteamine in the range of 6.5–18 GHz (46.12–16.66 mm) and 59.6–120.0 GHz (5.03–2.72 mm), respectively. We used a deep spectral line survey toward the molecular cloud G+0.693–0.027 obtained with the IRAM 30 m and Yebes 40 m radiotelescopes to search for cysteamine. Results. We assigned 815 rotational transition lines of five conformers (gGt, gGg, g 0Gg, g 0Gg 0 , and g 0Gt) to fit the rotational constants, quartic centrifugal distortion constants, and the 14N nuclear quadrupole coupling constants. For four conformers (gGt, gGg, g 0Gg, and g 0Gg 0 ), the 34S isotopologs were observed, and for two of them (gGg and g 0Gg), the 13C and 15N isotopolog spectra were also detected; all in natural abundance. The five conformers of cysteamine were not detected toward the G+0.693-0.027 molecular cloud. We derived upper limits for their molecular abundances compared to molecular hydrogen of <(0.2−1.3) × 10−10. The relative abundances with respect to the oxygen counterpart ethanolamine, previously detected toward this cloud, are NH2CH2CH2OH/NH2CH2CH2SH > 0.8–5.3.
