Extension of 2-Ethoxyethanol Rotational Spectroscopy and Its Search in the Interstellar Medium

Abstract Motivated by the recent detections of related alkoxy alcohols in the interstellar medium (ISM), we conducted a rotational spectroscopic study of 2-ethoxyethanol (C 2 H 5 OCH 2 CH 2 OH) to enable its search in the ISM. Quantum chemical calculations were performed to identify the lowest-energy conformers and predict their spectroscopic parameters. The rotational spectrum of the most stable conformer, −sc +sc ap ap-, was measured using complementary spectrometers covering the frequency regions 2–20, 6.5–18, 150–220, 230–330, and 370–500 GHz. A total of 2628 distinct transitions were assigned and fitted using a Watson A-reduced Hamiltonian, allowing the determination of rotational and centrifugal distortion constants up to the octic level. The resulting spectroscopic predictions are suitable for astronomical observations in the (sub)millimeter-wave domains. Using these new data, a search for −sc +sc ap ap- 2-ethoxyethanol was carried out toward NGC 6334I using Atacama Large Millimeter/submillimeter Array (ALMA) observations. No detection was obtained, and an upper limit column density of 1.1 × 10 17 cm −2 was derived.