Ice chemistry

Low Energy Ion Scattering Mass Spectrometer (LEIS)-1

High Resolution Transmission Electron Microscope (HRTEM) with EDAX

Instrument specification

The instrument consists of three ultrahigh vacuum chambers (made from non-magnetic stainless steel) named as the ionisation, the octupole, and the scattering chambers. These chambers are fitted with several turbomolecular pumps (Pfeiffer Vacuum) and backed by dry pumps (Pfeiffer Vacuum).

The scattering chamber is cylindrical in shape, with 15 inches in length, and 13 inches in diameter. This scattering chamber is fitted with a sample manipulator on which a closed cycle helium cryostat is mounted from the top, and with various probes focussing on the centre, at the substrate, Ru(0001).

Two pressure sensors, ionisation gauges of Bayard-Alpert type (B-A gauge, model no. PBR 260) are attached in the ionisation and scattering chamber. They are controlled by a ‘MaxiGauge’ vacuum gauge controller (Pfeiffer, Model TPG 256 A). An ultimate pressure below 5 × 10-10 mbar (limit of the controller) is achieved in both the ionisation and scattering chambers after bake-out. During the experiment, vapors of the desired molecules (like water and carbon monoxide) are introduced into the scattering chamber through two all-metal leak valves (Pfeiffer vacuum). A separate line is connected to the ionization chamber also to introduce gases into the chamber for ionization using an all-metal leak valve (Kurt J Leskar).

Technical Capabilities

This instrument is designed to study ice surfaces relevant to terrestrial and extra-terrestrial environments. The basic conditions prevailing in outer space are ultrahigh vacuum with a base pressure range <10-12 torr, and low temperatures, in the range of 5-200 K. The whole instrument is maintained at ultrahigh vacuum with several vacuum pumps connected in series. There is a target substrate of Ru(0001) single crystal (Princeton Scientific Corp.) inside the chamber which can be cooled to a temperature as low as 8 K using a closed cycle helium cryostat connected with a temperature controller and heater. It can maintain any temperature of interest. Thin layers of various molecular solid (ice) surfaces, such as water, alcohols, carbon monoxide etc., can be created by vapor depositing on the precooled single crystal substrate. The reactivity of such a molecular solid surface is probed by various techniques.

Low energy ion scattering mass spectrometry is one of those. This technique uses reactive ions produced by electron impact ionization (EI) which are then mass and energy selected by quadrupole mass analyzer and subjected to collide on the desired molecular solid surfaces. The scattered ions from the surfaces are analysed by another quadrupole mass spectrometer. Together with this, we have a temperature-programmed desorption mass spectrometer (TPD-MS) to probe the surface desorbing species, a low-energy alkali-ion gun to trigger out the neutral species present on the surface, and a reflection absorption infra-red spectrometer (RAIRS) for getting the infra-red spectrum of surface species. To study the photochemistry of the ice, this instrument is equipped with a vacuum ultraviolet source (Deuterium lamp with magnesium fluoride window).

Schematic of the ice instrument

High Resolution Transmission Electron Microscope (HRTEM) with EDAX

Schematic diagram of the experimental setup. This instrument is discussed in detail by Vishwakarma, G. et al. J. Phys. Chem. Lett. 14, 2823–2829 (2023).

Key features of LEIS technology

  • Low energy ion scattering mass spectrometer (LEIS-MS)
  • Temperature-programmed desorption mass spectrometer (TPD-MS)
  • Reflection Absorption Infrared Spectrometer (RAIRS)
  • Low energy alkali ion gun (Cs+/Li+)
  • Metal evaporator
  • Vacuum Ultraviolet (VUV) light (Deuterium lamp)

Ultra Low Energy Ion Scattering Mass Analyser

This instrument is designed to study ice surfaces relevant to terrestrial and extraterrestrial environment. The basic conditions prevailing there in outer space are ultra high vacuum (base pressure range < 10-12 torr) and low temperature of the range of 5-200 K. The whole instrument maintained at ultra high vacuum (UHV) with several vacuum pumps connected in series. There is a target of Ru(0001) single crystal (Princeton Scientific Corp.) inside the chamber which can be cooled to a temperature as low as 8 K using a closed cycle helium cryostat connected with a temperature controller and heater to maintain any temperature of interest. Thin layers of various molecular solid (ice) surfaces such as water, alcohols, carbon monoxide etc. are developed by vapour depositing on the precooled single crystal substrate. The reactivity of such a molecular solid surfaces probed by various techniques. Low energy ion scattering mass spectrometry is one of those. The technique uses reactive ions produced by electron impact ionization (EI) which are then mass and energy selected by quadrupole mass analyzer and subjected to collide on the desired molecular solid surfaces. The scattered ions from the surfaces are analysed by another quadrupole mass spectrometer. Together with this we have a temperature programmed desorption mass spectrometer (TPD-MS) to probe the surface desorbing species, low energy alkali-ion gun to trigger out the neutral species present on the surface, Reflection absorption infra-red spectrometer (RAIRS) for getting the infra-red spectrum of surface species.

Source of the components

Vacuum components: Pfeiffer Vacuum GmbH, Germany

Reflection absorption IR spectrometer: Bruker Optik GmbH, Vertex 70

Low energy alkali-ion gun: Kimball Physics Inc, USA

Closed cycle He cryostat: ColdEdge Technologies, USA

Deuterium source: McPherson, USA

Notable mentions from our group

High Resolution Transmission Electron Microscope (HRTEM) with EDAX

References

  1. Clathrate hydrates in interstellar environment, Jyotirmoy Ghosh, Rabin Rajan J. Methikkalam, Radha Gobinda Bhuin, Gopi Ragupathy, Nilesh Choudhary, Rajnish Kumar, and Thalappil Pradeep, Proc. Natl. Acad. Sci. U.S.A., 116 (2019) 1526-1531 (DOI: 1073/pnas.1814293116).
  2. Formation of cubic ice via clathrate hydrate, prepared in ultrahigh vacuum under cryogenic conditions, Jyotirmoy Ghosh, Radha Gobinda Bhuin, Gaurav Vishwakarma, and Thalappil Pradeep, J. Phys. Chem. Lett., 11 (2020) 26-32 (DOI: 1021/acs.jpclett.9b03063).
  3. Iron assisted formation of CO2over condensed CO and its relevance to interstellar chemistry, Rabin Rajan J. Methikkalam, Jyotirmoy Ghosh, Radha Gobinda Bhuin, Soumabha Bag, Gopi Ragupathy, and Thalappil Pradeep, Phys. Chem. Chem. Phys., 22 (2020) 8491-8498 (DOI: 1039/c9cp06983f).
  4. Interaction of acetonitrile with water-ice: An infrared spectroscopic study, Radha Gobinda Bhuin, Rabin Rajan J. Methikkalam, Bhalamurugan Sivaraman and Thalappil Pradeep, J. Phys. Chem. C, 119 (2015) 11524-11532 (DOI: 1021/jp512607v).
  5. Development of ultralow energy (1-10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids, Soumabha Bag, Radha Gobinda Bhuin, Rabin Rajan J. Methikkalam, Luke Kephart, Jeff Walker, Kevin Kuchta, Dave Martin, Jian Wei and Thalappil Pradeep, Rev. Sci. Instrum., 85 (2014) 014103 (DOI: 1063/1.4848895).
  6. Induced migration of COfrom hydrate cages to amorphous solid water under ultrahigh vacuum and cryogenic conditions, Gaurav Vishwakarma, Bijesh Malla, Karri Sesha Surya Vara Prasad Reddy, Jyotirmoy Ghosh, Soham Chowdhury, Sharma S. R. K. C. Yamijala, Sandeep Kumar Reddy, Rajnish Kumar, and Thalappil Pradeep, Phys. Chem. Lett. 2023, 14 2823–2829 (DOI: 10.1021/acs.jpclett.3c00373).
  7. Existence of acetaldehyde clathrate hydrate and its dissociation leading to cubic ice under ultrahigh vacuum and cryogenic conditions, Gaurav Vishwakarma, Bijesh K. Malla, Soham Chowdhury, Sakshi Pradip Khandare and Thalappil Pradeep, J. Phys. Chem. Lett. 2023, 14, 5328–5334. (DOI:10.1021/acs.jpclett.3c01181)
Low Energy Ion Scattering Mass Spectrometer (LEIS)-2

Low Energy Ion Scatter...

Low Energy Ion Scattering Mass Spectrometer (LES) is a custom built instrument in our laboratory to probe chemical reactions that occur on the surface of ice.

Read more
Low Energy Ion Scattering Mass Spectrometer (LEIS)-1

Low Energy Ion Scatter...

This instrument is designed to study ice surfaces relevant to terrestrial and extra-terrestrial environments. The basic conditions prevailing in outer space are ultrahigh vacuum with a base pressure range <10-12 torr, and low temperatures, in the range of 5-200 K. The whole instrument is maintained at ultrahigh vacuum with several vacuum pumps connected in series.

Read more

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