2024-03-28T09:48:27Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1462672022-11-22T10:31:56Zcom_10261_135com_10261_4col_10261_388
00925njm 22002777a 4500
dc
Martín-Doménech, R.
author
Manzano-Santamaría, J.
author
Muñoz-Caro, Guillermo M.
author
Cruz-Díaz, Gustavo A.
author
Chen, Y.-J.
author
Herrero, Víctor J.
author
Tanarro, Isabel
author
2015-11-13
Context. Ice mantles that formed on top of dust grains are photoprocessed by the secondary ultraviolet (UV) field in cold and dense molecular clouds. UV photons induce photochemistry and desorption of ice molecules. Experimental simulations dedicated to ice analogs under astrophysically relevant conditions are needed to understand these processes. Aims. We present UV-irradiation experiments of a pure CO2 ice analog. Calibration of the quadrupole mass spectrometer allowed us to quantify the photodesorption of molecules to the gas phase. This information was added to the data provided by the Fourier transform
infrared spectrometer on the solid phase to obtain a complete quantitative study of the UV photoprocessing of an ice analog. Methods. Experimental simulations were performed in an ultra-high vacuum chamber. Ice samples were deposited onto an infrared transparent window at 8K and were subsequently irradiated with a microwave-discharged hydrogen flow lamp. After irradiation, ice samples were warmed up until complete sublimation was attained. Results. Photolysis of CO2 molecules initiates a network of photon-induced chemical reactions leading to the formation of CO, CO3, O2, and O3. During irradiation, photon-induced desorption of CO and, to a lesser extent, O2 and CO2 took place through a process called indirect desorption induced by electronic transitions, with maximum photodesorption yields (Ypd) of ∼1.2 × 10−2 molecules incident photon−1, ∼9.3 × 10−4 molecules incident photon−1, and ∼1.1 × 10−4 molecules incident photon−1, respectively. Conclusions. Calibration of mass spectrometers allows a direct quantification of photodesorption yields instead of the indirect values that were obtained from infrared spectra in most previous works. Supplementary information provided by infrared spectroscopy leads to a complete quantification, and therefore a better understanding, of the processes taking place in UV-irradiated ice mantles. © ESO 2015
Astronomy & Astrophysics, 584: A14 (2015)
0004-6361
http://hdl.handle.net/10261/146267
10.1051/0004-6361/201526003
1432-0746)
http://dx.doi.org/10.13039/501100003329
ISM: molecules
ISM: clouds
Methods: laboratory: solid state
Techniques: spectroscopic
UV photoprocessing of CO2 ice: a complete quantification of photochemistry and photon-induced desorption processes*