Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (C3H7X; X = CN, OH, HCO) at 157 nm Exploiting an Ultracompact Velocity Map Imaging Spectrometer: The (Iso)Propyl Channel

The photodissociation dynamics of astrophysically relevant propyl derivatives (C3H7X; X = CN, OH, HCO) at 157 nm exploiting an ultracompact velocity map imaging (UVMIS) setup has been reported. The successful operation of UVMIS allowed the exploration of the 157 nm photodissociation of six (iso)propyl systems-n/i-propyl cyanide (C3H7CN), n/i-propyl alcohol (C3H7OH), and (iso)butanal (C3H7CHO)-to explore the C3H7 loss channel. The distinct center-of-mass translational energy distributions for the i-C3H7X (X= CN, OH, HCO) could be explained through preferential excitation of the low frequency C-H bending modes of the formyl moiety compared to the higher frequency stretching of the cyano and hydroxy moieties. Although the ionization energy of the n-C3H7 radical exceeds the energy of a 157 nm photon, C3H7+ was observed in the n-C3H7X (X = CN, OH, HCO) systems as a result of photoionization of vibrationally hot n-C3H7 fragments, photoionization of i-C3H7 after a hydrogen shift in vibrationally hot n-C3H7 radicals, and/or two-photon ionization. Our experiments reveal that at least the isopropyl radical (i-C3H7) and possibly the normal propyl radical (n-C3H7) should be present in the interstellar medium and hence searched for by radio telescopes.

Automated summary

In this study, the photodissociation dynamics of astrophysically relevant propyl derivatives at 157 nm has been explored using an ultracompact velocity map imaging setup. The results show distinct center-of-mass translational energy distributions, indicating preferential excitation of low frequency C-H bending modes. C3H7+ was observed, suggesting the presence of isopropyl and possibly normal propyl radicals in the interstellar medium.