Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (C 3 H 7 X; 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 (C 3 H 7 X; 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 (C 3 H 7 CN), n/i -propyl alcohol (C 3 H 7 OH), and (iso)butanal (C 3 H 7 CHO)─to explore the C 3 H 7 loss channel. The distinct center-of-mass translational energy distributions for the i -C 3 H 7 X (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 -C 3 H 7 radical exceeds the energy of a 157 nm photon, C 3 H 7 + was observed in the n -C 3 H 7 X (X = CN, OH, HCO) systems as a result of photoionization of vibrationally "hot" n -C 3 H 7 fragments, photoionization of i -C 3 H 7 after a hydrogen shift in vibrationally "hot" n -C 3 H 7 radicals, and/or two-photon ionization. Our experiments reveal that at least the isopropyl radical ( i -C 3 H 7 ) and possibly the normal propyl radical ( n -C 3 H 7 ) should be present in the interstellar medium and hence searched for by radio telescopes.