Space and laboratory observation of the deuterated cyanomethyl radical HDCCN (C. Cabezas et al., A&A, 02/2021)

• HDCCN (forest of lines) – New detection in TMC-1, laboratory production and full spectroscopically characterization of the singly deuterated isotopolog of H₂CCN

• Deuteration is driven by deuteron transfer from the H₂D⁺ molecular ion
• Further constraints on molecular formation pathways and identification of U-lines in molecular surveys

A study of C₄H₃N isomers in TMC-1: line by line detection of HCCCH₂CN (N. Marcelino et al., A&A, 02/2021)

• HCCCH₂CN (22 lines) – New detection and confirmation
• CH₂CCHCN (16 lines) – New detection and confirmation

• The derived abundances suggest a common origin in the formation of the C₄H₃N isomers: reaction of the CN radical with unsaturated hydrocarbons methyl acetylene and allene

Discovery of the acetyl cation, CH₃CO⁺, in space and in the laboratory (J. Cernicharo et al., A&A, 02/2021)

• CH₃CO⁺ (8 lines) – First time detection in Space (TMC-1 and other cold dark clouds), laboratory production and characterization of the protonated form of ketene (H₂CCO)

• The derived high abundance of the protonated form of ketene is due to the high proton affinity of the neutral species
• Further constraints on formation/destruction rates and/or chemical formation routes to CH₃CO⁺
• The reaction of ketene with H₃⁺ is the most favourable for protonation, from the thermodynamical point of view

Space and laboratory discovery of HC₃S⁺ (J. Cernicharo et al., A&A, 02/2021)

• HC₃S⁺ (4 lines) – First time detection in Space (TMC-1), laboratory production and characterization of the protonated form of C₃S

• The spectroscopic parameters obtained for HC3S+ from ab initio calculations agree very well with that obtained from observations and in the laboratory
• Constraint in chemical formation routes: The derived C₃S/HC₃S⁺ ratio is well reproduced by a gas-phase chemical model in which HC₃S⁺ is mostly formed through protonation of C₃S and the reactions S⁺ + C₃H₂ and S + C₃H₃⁺

Tentative detection of HC₅NH⁺ in TMC-1 (N. Marcelino et al., A&A, 11/2020)

• HC₅NH⁺ (7 lines in Q band) – First time detection in Space

• Existence of additional formation routes at stake: Our pseudo time-dependent gas-phase chemical models of cold dark clouds underestimate the abundance of protonated molecules

Discovery of HC₃O⁺ in space: The chemistry of O-bearing species in TMC-1 (J. Cernicharo et al., A&A, 10/2020)

• HC₃O⁺ (4 lines) – First time detection in Space and laboratory characterization of the protonated form of C₃O

• The high abundance of the protonated form of C₃O, (HC₃O⁺) is due to the high proton affinity of the neutral species
• Reactions between hydrocarbon ions and atomic oxygen probably participate in the growth of these long O-bearing carbon chains (e.g. c-H₂C₃O and HCCCHO)
• Existence of additional formation routes at stake: Our pseudo time-dependent gas-phase chemical models of cold dark clouds underestimate the abundance of protonated molecules

Discovery of HC₄NC in TMC-1: A study of the isomers of HC₃N, HC₅N and HC₇N (J. Cernicharo et al., A&A, 10/2020)

• HC₄NC (5 lines, Q band) – First time detection in Space

• Cold molecular clouds favor the formation of metastable isomers due to their low temperatures.
• In the ejecta of AGB stars, where the temperature is higher, the presence of high-energy isomers is less favorable because chemical reactions, including isomerization, are expected to favor the most stable isomer. The same pattern is expected for isotopic fractionation