J/A+A/647/A127 The C+ ion photofragment spectra (Guan+, 2021)
Photodissociation branching ratios of 12C16O from 110500 to
113045 cm-1: first observation of the C(1S) channel.
Guan L., Jiang P., Zhang G., Yin T., Cheng M., Gao H.
<Astron. Astrophys. 647, A127 (2021)>
=2021A&A...647A.127G 2021A&A...647A.127G (SIMBAD/NED BibCode)
ADC_Keywords: Ultraviolet ; Spectroscopy
Keywords: molecular data - comets: general -
planets and satellites: atmospheres - Sun: UV radiation -
ISM: molecules
Abstract:
Carbon monoxide (CO) is one of the most abundant molecular species in
comets. Its photodissociation by the solar radiation in the vacuum
ultraviolet (VUV) region produces excited atomic fragments C(1D),
C(1S), and O(1D), which radiate at characteristic wavelengths when
they decay to lower states. The fractional rate constants for
generating these fragments from CO photodissociation under the entire
range of the solar radiation field are key input values in modelling
the observed atomic emission intensities from comets. In this study,
the branching ratios of the four lowest dissociation channels
C(3P)+O(3P), C(1D)+O(3P), C(3P)+O(1D), and C(1S)+O(3P)
of the 12C16O photodissociation are measured in the VUV energy
range between the threshold of producing the C(1S)+O(3P) channel
(∼110500cm-1) and the ionisation energy (IE) of 12C16O
(∼113045cm-1). We measured these ratios using the VUV time-slice
velocity-map ion imaging apparatus. We observe a number of high
Rydberg states in the aforementioned energy range, with most of them
mainly producing ground C(3P) and O(3P) atomic fragments, and only
a few of them producing a significant amount of excited C(1D) or
O(1D) fragments. We also observe the excited C(1S) fragment from
CO photodissociation and measured its branching ratio for the first
time. Based on the photodissociation branching ratios measured in the
current and previous studies, we are able to estimate the relative
percentages of the excited atomic fragments C(1D), C(1S), and
O(1D) from the solar photolysis of 12C16O below its IE. We
discuss the implications for the photochemical modelling of the
CO-dominated comet C/2016 R2 (Pan-STARRS).
Description:
This is the overall C+ ion photofragment spectra of 12C16O
obtained in the VUV energy region from 110500cm-1 to 113045cm-1.
Several different laser dyes are used, because no single laser dye can
cover the whole energy range. We directly connected several segments
of spectra collected by using different laser dyes without calibrating
their relative intensities. Thus, only the peak positions and line
widths are useful here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectrum.dat 15 2650 C+ ion photofragment spectrum
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Byte-by-byte Description of file: spectrum.dat
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Bytes Format Units Label Explanations
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1- 8 F8.1 cm-1 lambda VUV frequency
10- 15 F6.1 --- Int Intensity
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Acknowledgements:
Hong Gao, honggao2017(at)iccas.ac.cn
(End) Patricia Vannier [CDS] 27-Jan-2021