J/A+A/671/A51 Rate coefficients for H2O + H2O collisions (Mandal+, 2023)
Rate coefficients for rotational state-to-state transitions in H2O + H2O
collisions for cometary and planetary applications, as predicted by mixed
quantum-classical theory.
Mandal B., Babikov D.
<Astron. Astrophys. 671, A51 (2023)>
=2023A&A...671A..51M 2023A&A...671A..51M (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Comets ; Planets ; Spectra, millimetric/submm
Keywords: molecular data - submillimiter: general - comets: general -
ISM: molecules - planets and satellites: fundamental parameters -
astronomical databases: miscellaneous - comets: general
Abstract:
We present new calculations of collision cross sections for
state-to-state transitions between the rotational states in
H2O + H2O system, that are used to generate new database of
collisional rate coefficients for cometary and planetary applications.
Calculations are carried out using mixed quantum/ classical theory
approach implemented in MQCT code. Large basis set of rotational
states used in these calculations permits to predict thermally
averaged cross sections for 441 transitions in para- and ortho-H2O
in a broad range of temperatures. It is found that all state-to-state
transitions in H2O + H2O system split onto two well defined
groups, one with larger values of cross sections and smaller energy
transfer, that corresponds to the dipole-dipole driven processes, are
the other with smaller cross sections and larger energy transfer,
driven by higher-order interaction terms. Detailed analysis of
theoretical error bars is presented, and symmetrization of
state-to-state transition matrixes is carried out to ensure that
excitation and quenching processes for each transition satisfy the
principle of microscopic reversibility. Comparison with other data
available from literature for H2O + H2O collisions is also
presented.
Description:
This program calculates Thermally Averaged Cross Sections (TACS) for
transitions in H2O + H2O at any given temperature in the range
between T=150K and 800K, by numerical qubic spline interpolation
between six pre-computed data points. The unit of input temperature is
K and the unit of output TACS is Angstrom^2. The driver program is in
the file named "Generate_TACS.f90". User needs to indicate the value
of temperature by assigning the value of variable "req_temp". The
interpolated TACS for all transitions will be printed in the file
named "Output_TACS.out". The output file first lists j, ka and kc for
the initial state followed by the same for the final state. The TACS
are printed at the end of the line.
In the "Makefile", user can indicate any standard Fortran compiler.
To compile and execute:
$ make
$ ./compute_tacs
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
Generate_TACS.f90 105 25 Driver program
MQCT_TACS.dat 69 5304 Precomputed TACS for 441 transitions at
six values of temperature
Makefile 33 4 Makefile
engines.f90 512 18 Cubic spline interpolation code
--------------------------------------------------------------------------------
Acknowledgements:
Dmitri Babikov, dmitri.babikov(at)mu.edu
(End) Dmitri Babikov [Marquette University], Patricia Vannier [CDS] 24-Jan-2023