Experimental study on photochemistry of water and CO molecules on silicate dust

2019 Fiscal Year Research-status Report

• Project/Area Number: 19K23449
• Research Institution: Hokkaido University
• Principal Investigator: NGUYEN THANH 北海道大学, 低温科学研究所, 博士研究員 (40846599)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: Chemical desorption / chemican reaction / amorphou silicate / experiments / dust grains / interstellar medium

Outline of Annual Research Achievements

By using ASURA system, I performed the experiments of the photolysis of H2O and CO on the amorphous silicate (Mg2SiO4) held at different temperatures. Firstly, I performed the photolysis of H2O on Mg2SiO4 at low temperatures. H2O decreases with increasing of photo exposure times due to destruction by the following reactions: H2O + hv -> OH + H (1)and H2O + hv -> H2 + O (2). I obtained the photodesorption of CI was better than porous and np-ASW on the silicate substrate at low temperatures. Secondly, I investigated the photochemical reactions of a mixture CO and H2O on the silicate substrate at low temperatures. There were the chemical reactions occurring on the surface via the reactions (1) and (3): OH+CO->CO2+H (3). I obtained the formation of CO2 via FTIR spectra and TPD-QMS.

The effective photodesorption of H2O and CO2 on silicate substrate was presented via the proportional column density of H2O and CO2. However, the effect of the amorphous silicate substrate has not yet been clarified because there was the mixture between the products and contamination. I, therefore, have not concluded the effects of silicate substrate for photodesorption of water and the mixture of CO and H2O yet. I continuously study the effects of amorphous silicate on H2O, CO, and other species to clarify on the bare cosmic dust maintained at low temperatures after calibrating parameters.

Current Status of Research Progress

3: Progress in research has been slightly delayed.

Reason

I should calibrate the machine parameters as the pressure, temperature, power, etc.

In addition, I calibrate the parameters for the experiments such as the monolayer of species, the thickness of water ice substrate as well as the duration for one experiment to obtain the exactly results.

In order to get the better data, I should carry out and repeat the experiments in a long time. After that, I need taking time to analyze the results that I obtained from the experiments, simultaneously, I should compare the results with the relevant literatures to give the better conclusions.

Strategy for Future Research Activity

The aim is to study the effect of amorphous silicate to the chemical reactions and desorption of species on interstellar dust grains in the interstellar medium. Therefore, I continuously survey the chemical reactions of molecular species on amorphous silicate at different temperatures. Products will analyze by FTIR spectra and TPD-QMS.

Firstly, I will perform the experiments relative to phosphorus bearing (P-bearing) species, for instance, PH3 or PO, on water ice such as porous ASW and non-porous ASW. The purpose is to indicate the chemical desorption likely occurring on the water ice substrates implicated in the astrochemical environments.

Then, I will similarly investigate the chemical desorption of P-bearing species on amorphous silicate (Mg2SiO4) at low temperatures. It will be useful to indicate the pathways of chemical reactions of P-bearing species on bare cosmic dust. To give the best evidence for the affection of bare cosmic dust, I will compare the chemical desorption of P-bearing species between water ice and amorphous silicate. I expect the chemical reaction of P-bearing species on amorphous silicates and water ice substrates is due to the difference of binding energy, mechanisms of reactions, or the interaction between P-bearing species and various substrates.

Causes of Carryover

I canceled some international conference, therefore, there is still the remaining amount of money from last year. However, I will use the total amount of money for this year.