Astrophysical observations provide the signature of the physical and chemical processes occurring under extreme physical conditions in terms of density, temperature and irradiation. As thermal equilibrium conditions are scarcely fulfilled, individual microscopic atomic and molecular processes involved in excitation, ionization and reactivity directly impact the composition and temperature of the environments.

My talk will describe some recent new detections illustrating different aspects of molecular astrophysics:

1. The recent detection of HeH+ in the NGC7027 planetary nebula [1], confirming predictions made more than 3 decades ago [2] and its role as the first molecule predicted by models of the Early Universe

2. The laboratory efforts and theoretical debates following the tentative identification of the C3H+ molecular ion [3]

3. The puzzling chemical questions raised by the detection of the first doubly sulfuretted molecule S2H in the Horsehead nebula [4]

References

[1] "Astrophysical detection of the helium hydride ion HeH+" Gusten et al. 2019, Nature 568, 357

[2] "Molecules in planetary nebulae"  Black 1978, ApJ 222, 125

"On the formation and destruction of HeH+ in planetary nebulae and the associated infra-red emission line spectrum" Flower & Roueff 1979, A&A 72, 361

[3] "The IRAM-30 m line survey of the Horsehead PDR II. First detection of the l-C3H+ hydrocarbon cation"

Jerome Pety et al. 2012, A&A 548, A68  

[4] "First Interstellar Detection of S2H" Asuncion Fuente et al. 2017, , ApJ 851, L49  dans le vide des composants de masse négative.