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the deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation

by:Top-In     2020-01-13
The original carbon chondrite contains a large number of organic compounds mainly composed of refractory organic matter (IOM).
A notable feature of this IOM is the systematic enrichment in tritium compared to the solar hydrogen reservoir.
This concentration is considered a low signTemperature ion-Molecules or gasesGrain reaction.
However, the extent of the influence of solar system processes, especially ionising radiation, on the D/H ratio is largely unknown.
Here, we report the effect of electron irradiation on the hydrogen isotope composition of organic pioneers containing different functional bases.
From the initial composition of the land, the total D-
Enrichment and differential intra-molecular separation were induced in comparison with measurements in Orgueil meteorites.
Therefore, the ionization radiation can quantitatively explain the life-threatening process of organic matter in some carbon chondrites.
For these meteorites, the predecessor of IOM may have the same isotope composition as the main reservoir of the inner solar system.
Preparation of PS samples by spin
Coating Deposition on silicon wafers.
Rotating coating is a centrifugal force
Driving method for film deposition on a plane substrate.
Deposition is achieved by the rotation of the substrate, spreading a small amount of dissolved film on the substrate.
PS dissolved in toluene.
The speed is 2,000 miles. p. m.
The concentration in toluene is 10 wt % PS, and the final thickness is 1.
3 μm was obtained.
After deposition, the sample is stored for several hours under secondary vacuum conditions to ensure complete evaporation of toluene and polymerization of the film.
PE samples from 10-μm-thick film (
Cambridge Limited)
And mount to the brass sample holder using a conductive copper tape.
There are 900 pets in this pet. nm-
Two-way semi-directional thick filmcrystalline (
Good partner company)
And deposited on the brass sample holder.
Electron irradiation experiments were carried out on Hitachi s4 700 field
A scanning electron microscope with a firing gun is at 30 kV (
Institute of electronic microscope, University of Lille 1).
The electron flux was measured with the Faraday cup.
The start time of PE melting is usually lower than 80 °c.
After irradiation, there were no signs of degradation in the film.
Therefore, we can estimate that the temperature of the sample under the electron beam is between 20 and 80 °c.
Between the irradiation experiments and the different analytical steps, all samples are stored under dry ar flows in the dark.
UV irradiation on PET film.
Performed with a multi-color UV lamp (
Binsong irradiation system)
With a band-
Pass the filter at 239nm.
At this wavelength, the coupling between UV and PET film is particularly effective.
The lamp with nominal energy is 300 kWh W kWh cm.
However, the filter absorbs 239 of the injected energy at 80% nm, so in these experiments, the actual energy of the lamp is estimated to be 60 μW cm.
The modification caused by electron irradiation is proportional to the energy deposited in the sample. The fluence (
That is, the number of electrons per unit)
It is an important parameter for determining the electron deposition energy in the target sample.
Electronic injection measurement and Faraday Cup accuracy of ± 15% ().
For irradiation performed at 30 K electron volts, the energy is not completely dissipated in the film because the path followed by the electron is longer than the thickness of the PE and PS samples (
Penetration depth up to 17.
2 μm at 30 K electron volts, see).
In addition, we calculated the energy deposition of the first few hundred nanometers, which is the typical thickness measured by D/H for nano-simulation analysis.
The energy deposited in the film depends directly on the electronic stop power (
That is, the linear rate of energy transfer between the incoming particle and the target).
Here, get the characteristic electronic path and stop power from the ESTAR database ().
To take into account both the injection amount and the stop power, all isotope and structural data are shown as: a function of the electronic dose (eVu2009cm)
Is the electronic stop power supply (MeVu2009cm)
Is the amount of injection (eu2009cm).
UV irradiation uses a similar method to directly compare the effects of UV and electronic irradiation as a function of the energy deposited on PET Films.
The absorption coefficient here is 2.
For photons with a wavelength of 239 nm, select 5 × 10 cm (ref. ).
The calculated deposition energy after irradiation of 26 km/h is 3.
The 1 × 10 evcm cm in the first 100 nm of PET film is a typical thickness for nano-simulation analysis.
The evolution of the molecular structure of the sample during irradiation was studied by infrared spectroscopy (FTIR)
Use an imaging spotlight 300 from Perkin
Elmer 1 at the University of Lille UMET.
The transmission spectrum was collected by averaging 32 scans in the range of 750-4,000 cuccm.
Linear baseline correction is performed for each spectrum between 750 and 3,700 cm.
Use Gaussian de-convolution (
Commercial Peakfit software for Bharat software, Inc.
For this purpose).
For PS films, the presence of interference stripes complicates the IR spectrum.
These stripes are usually produced by thin samples (1. 3u2009μm)
Synthesis by rotation
Coating deposition.
The substrate and film act as a plane parallel interface from which interference patterns can be generated (
Sine wave)arise.
These disturbances (
A sine contribution)
Remove from the normal spectrum using traditional subtraction.
For all irradiated samples, a clear signal of adsorption water is observed on the surface of the film ().
In addition, in the case of PE, the infrared spectrum in the range of 750-1,750 cuccm, according to the existing literature, presents additional optical features that cannot be attributed to any vibration pattern.
These features and the spectral contribution of the adsorption water make the analysis of structural changes very complicated and necessarily qualitative.
For this reason, we only pay attention to the normalized evolution of the main characteristic peak regions of each polymer, not to the peaks that are not attributable, nor to the peaks that originate from surface artifacts due to adsorption water
In the case of PE samples, before the quantitative Peak area, the typical band of the adsorption water is subtracted from the spectrum ().
All D/H analyses were performed on the Cameca nano SIMs 50 at MNHN in Paris, France.
The surface of the sample is gold-coated (20u2009nm thick)
Before the analysis, there was an electronic
A flood gun was used during the analysis.
The sample surface is scanned by a primary Cs beam on an area of 8 × 8 μm and divided into 64 × 64 pixels at a grating speed of 2 MS per pixel MS.
Collect isotopes from internal 5. 6 × 5.
In the 6 μm region in the multi-collection mode, the beam current is 16 pa.
Secondary ion of H-and D-
It was collected with a dead electron multiplier. time of 44u2009ns.
Set the mass resolution capability of the mass spectrometer to 4,000.
400-before each analysis-
The PA main beam is scanned at a surface area of 10 × 10 μm over a time of 50 μs to remove gold coating and surface contamination.
This process is particularly important for the removal of sample layers containing adsorbed water.
For this polymer, this pre-decomposition usually removes 50 nm of material before the analysis begins.
Instrument quality grading is corrected by measuring several times a day for unirradiated films used as internal standards.
When it comes to instrument drift, the daily measurement of type III natural cheese roots shows that the repeatability is ± 30 ‰.
Typical analyses included surround measurements of the irradiated areas in the nearby unirradiated areas.
The error bar reported in this study is an error based on the second sum of the standard deviations for non-repeated executionirradiated (
Three to four analysis)
And the radiation area (
Two to four analysis).
For each polymer, Delta relative to SMOW is determined by conventional gas source mass spectrometry before irradiation (
Performing at Nancy\'s CRPG)
PET, PS and PE were found to be-33 ± 8 ‰,-30 ± 10 ‰ and-76 ± 7 ‰, respectively ‰. The ToF-
SIMS spectral measurement is the use of flight time in positive mode-
V instrument for Sims (ION-
UCCS at Lille University.
The instrument is equipped with Bi liquid metal ion gun.
Pulse Bi primary ions for analysis (25u2009keV, 1u2009pA).
Obtain the surface spectrum from the region of 500 × 500 μm (
256x256 pixels-20 scans)
Then reconstruct the 100 × 100 u2009 μm region corresponding to irradiation and non-irradiation
Irradiation area.
The effect of charging, due to the primary ion, makes up for the use of low pulse
Energy Electronics (20u2009eV).
The C/H ratio of PS, PE and PET cannot be determined directly from the flight time
Mass spectrometry measurement.
Instead, we quantitatively compared the strength ratio of each irradiation point to the surrounding unirradiated material H/CH.
Use this selection of molecular fragments instead of simple ions (C)
Related to the analysis mode used for flight timeSIMS analysis.
There are two advantages to this setting.
First, it provides information on the evolution of the carbon skeleton through radiation (
People from H to CH).
After irradiation, the quality of light (
Short fragments corresponding to irradiated substances)
The heavier molecular fragments are richer ().
This is the direct result of the broken chain caused by irradiation.
Second, this setting reduces carbon. based (C)
Contamination during surface analysis.
For these reasons, the CH part was selected as the agent for recording the change of C/H ratio during irradiation.
Only the normalized quantity (
Relative to unirradiated samples)
It is provided here because the measured strength ratio cannot be directly compared with the true atomic C/H ratio.
Finally, with respect to isotope measurements, typical analyses include surround measurements of irradiation points and unirradiated areas.
The error bars in this study report are 1 s. d.
Non-repetitive s
Irradiation area (
Three to four analyses)
And apply the classical error propagation to the normalized value.
Organic free radical concentration from electron shunmagnetic resonance (EPR).
At LASIR, No. 1, Lille University, the EPR spectra were recorded with Bruker Elexsys E500, which works at 9 ghz.
The amplitude modulation and microwave power are set to 2g and 5 mw, respectively.
For ultraviolet radiation, the film of PET (6 × 6u2009mm size)
Direct irradiation of high sensitivity in transmission mode (TMHS)
Oral cavity through optical window.
The spin concentration is determined using a two-integral program using weak spacing.
Typically, the absolute error of spin concentration is better than 5% in this analytical configuration.
All structural, chemical and isotope changes presented in this study have common dynamics during irradiation. A first-
This change was successfully described.
Usually, the first one
The law of order rate associates the time derivative of a given species concentration with the instantaneous concentration passing through the time constant.
Since the electronic dose is a function of the equation of stopping power and electronic injection quantity (1)
The evolution of a quantity is described as a dose constant.
The integration of this relationship provides a pathway to quantitative evolution as an electronic dose function: where []
Is the initial strength of the polymer at a given feature at an increasing dose.
Different modes of change can be compared because the dose constant is the direct agent of the rate of change of the radiation molecule.
For this reason, we used the normalized quantity (
Peak area and ratio).
According to this fitting procedure, we determined the electronic dose required for each sample to reach the platform value of 90% ().
In turn, these doses are used as thresholds to determine the isotope features of each sample on the plateau.
All experiments performed at higher doses were considered to calculate characteristic isotope features on the plateau.
Usually, two data points for each polymer are located on the plateau.
The isotope platform values for each polymer are determined to be the mean value of the isotope data located on the plateau.
The error is used as 1 standard deviation for this data set.
On the Structure Evolution, the isotope data set shows the isotope platform ().
Isotope features of irradiated materials on their respective plateau (
Given relative to SMOW)
PE, PS and PET were 46 3 ± 3 ‰, 315 ± 30 ‰ and 27 2 ± 60 ‰, respectively ‰.
Then, assuming the local equilibrium under the electron beam, the isotope features of each C-H bond are determined.
A simple mass balance is considered because the initial relative ratio of the C-H Bond is known and all C-H groups are lost at comparable speeds during irradiation, as described above.
So, from these molecules Delta (
Relative to SMOW)
The in-molecule separation factor is easy to determine: the error of the ratio is transmitted to the value (quadratic sums)
The relative error of the factor was found to be less than 14%.
In the original planetary environment, the time scale required for radiation to reach a dose comparable to the dose studied here is determined from the measured now --
The daily energy distribution of the stationary solar flux.
This distribution follows a power law where it is low
Energy Electronics (
1 ~ 10 thousand electronic volts)
Richer than highenergy ones (). For the low-energy range (1–10u2009keV)
The integral flux and related electron dose rate are calculated (
Medium blue and red areas).
The star activity of the original star has been shown to be at least three orders of magnitude higher than today.
Therefore, we consider the electronic flux higher than the static current-
The daily solar flux has risen by three orders of magnitude.
In this case, it takes only hundreds of years to produce the same deposited energy as we experienced in our experimental radiation ().
Finally, the environment of the original planet is optical thick and cold.
Therefore, direct Electronics (photon or ion)
On a thin and warm layer on the surface of the disk, irradiation is basically effective.
Instead, dust will not be exposed to sun particles in places close to the middle plane.
However, due to the prediction of vertical motion in a turbulent disk, this shielding effect is inefficient.
The current model shows that Micron
The size of the dust on the disk may cost 5% of its life at a height where radiation is effective.
Therefore, the dose required to reach the platform value is fully compatible with the typical life of the disk.
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