We have measured the alignment A20 of K*(3p54s2 2P3/2) and the ratio of cross sections R0 = sigma (3/2)/ sigma (1/2) of fine structure states K*(3p54s2 2P3/2, 2P1/2) for electron impact excitation in the range of incident energy E0 = 31.4-500 eV. We have also calculated these quantities in the distorted wave Born approximation (DWBA) and the plane wave Born approximation (PWBA). There is good agreement between experiment and the present DWBA and PWBA values for the alignment A20 whereas earlier DWBA values by Pangantiwar and Srivastava (1987) deviate systematically from experiment for E0 < 100 eV. For the ratio of cross sections R0 the present DWBA values agree only qualitatively with the experiment for E0 < 100 eV.
The modelling of molecular excitation and dissociation processes relevant to astrochemistry requires the validation of theories by comparison with data generated from laboratory experimentation. The newly commissioned Ice Chamber for Astrophysics-Astrochemistry (ICA) allows for the study of astrophysical ice analogues and their evolution when subjected to energetic processing, thus simulating the processes and alterations interstellar icy grain mantles and icy outer Solar System bodies undergo. ICA is an ultra-high vacuum compatible chamber containing a series of IR-transparent substrates upon which the ice analogues may be deposited at temperatures of down to 20 K. Processing of the ices may be performed in one of three ways: (i) ion impacts with projectiles delivered by a 2 MV Tandetron-type accelerator, (ii) electron irradiation from a gun fitted directly to the chamber, and (iii) thermal processing across a temperature range of 20–300 K. The physico-chemical evolution of the ices is studied in situ using FTIR absorbance spectroscopy and quadrupole mass spectrometry. In this paper, we present an overview of the ICA facility with a focus on characterising the electron beams used for electron impact studies, as well as reporting the preliminary results obtained during electron irradiation and thermal processing of selected ices.
Graphic Abstract
The Ice Chamber for Astrophysics-Astrochemistry (ICA) is a new laboratory end station located at the Institute for Nuclear Research (Atomki) in Debrecen, Hungary. The ICA has been specifically designed for the study of the physico-chemical properties of astrophysical ice analogs and their chemical evolution when subjected to ionizing radiation and thermal processing. The ICA is an ultra-high-vacuum compatible chamber containing a series of IR-transparent substrates mounted on a copper holder connected to a closed-cycle cryostat capable of being cooled down to 20 K, itself mounted on a 360 ○ rotation stage and a z-linear manipulator. Ices are deposited onto the substrates via background deposition of dosed gases. The ice structure and chemical composition are monitored by means of FTIR absorbance spectroscopy in transmission mode, although the use of reflectance mode is possible by using metallic substrates. Pre-prepared ices may be processed in a variety of ways. A 2 MV Tandetron accelerator is capable of delivering a wide variety of high-energy ions into the ICA, which simulates ice processing by cosmic rays, solar wind, or magnetospheric ions. The ICA is also equipped with an electron gun that may be used for electron impact radiolysis of ices. Thermal processing of both deposited and processed ices may be monitored by means of both FTIR spectroscopy and quadrupole mass spectrometry. In this paper, we provide a detailed description of the ICA setup as well as an overview of the preliminary results obtained and future plans.
The angle-resolved Kr L2,3M4,5M4,5 Auger spectra induced by proton impact ionization were measured at 1, 2.6 and 3.6 MeV proton energies where high-resolution spectroscopy techniques have been applied. The Auger energies and relative line intensities are compared with different earlier experimental data as well as our numerical results which have been obtained within a multiconfigurational Dirac-Fock approach. The alignment parameter 20 of the singly ionized krypton atoms has been extracted from the experimentally accessible anisotropy parameter A2 applying a special method, using the theoretical values of the angular distribution parameter 2 .
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