J/A+A/678/A51 Rate coefficients for H2O + H2O collisions (Mandal+, 2023)
Improved temperature dependence of rate coefficients for rotational
state-to-state transitions in H2O + H2O collisions.
Mandal B., Babikov D.
<Astron. Astrophys. 678, A51 (2023)>
=2023A&A...678A..51M 2023A&A...678A..51M (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Comets ; Planets ; Spectra, millimetric/submm
Keywords: molecular data - molecular processes -
astronomical databases: miscellaneous - comets: general -
planets and satellites: atmospheres - ISM: molecules
Abstract:
We present an improved database of temperature dependent rate
coefficients for rotational state-to-state transitions in H2O+H2O
collisions. The database includes 231 transitions between the lower
para- and 210 transitions between the lower ortho-states of H2O (up
to j=7) and can be employed for cometary and planetary applications up
to the temperature of 1000K. New general method is developed and
applied which permits to generate rate coefficients for excitation and
quenching processes that automatically satisfy the principle of
microscopic reversibility and, also, helps to cover the range of low
collision energies by interpolation of cross sections between the
process threshold and the computed data points. It is found that in
the range of intermediate temperatures, 150<T<600K, new rate
coefficients are in good agreement with those reported earlier, but
for higher temperatures, 600<T<1000K, the new revised temperature
dependence is recommended. The low temperature range, 5<T<150K, is now
covered, by the abovementioned interpolation of cross sections down to
the process threshold.
Description:
This program calculates Rate Constants for transitions in H2O+H2O at
any given temperature in the range between T=10K and 1000K, by
analytical exponential functions, and numerical qubic spline
interpolation. The unit of input temperature is K and the unit of
output Rate Constant is cm3/s. The driver program is in the file
named "Generate_Rates.f90". User needs to indicate the value of
temperature by assigning the value of variable "req_temp". The
computed Rate Constants for all transitions will be printed in the
file named "RatesforT_300.00000K.out" (where the 300.00000 is the
value of req_temp). The output file first lists j, ka and kc for the
initial state followed by the same for the final state. The Rate
Constants are printed at the end of the line for the Quenching and
Excitation processes, respectively.
In the "Makefile", user can indicate any standard Fortran compiler.
To compile and execute:
$ make
$ ./compute_rate
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
Makefile 34 4 Makefile
Generate_Rates.f90 99 27 Driver program
MQCT_TACS.dat 69 5304 Precomputed TACS for 441 transitions at
six values of temperature
engines.f90 178 792 Exponential extrapolation and
cubic spline interpolation code
CheckHighEnergy.dat 2 441 Initialization check for TACS data
CheckLowEnergy.dat 2 2646 Initialization check for TACS data
paraWaterEnergies.dat 50 316 Quantum numbers and energies of
para-H2O rotational states
orthoWaterEnergies.dat 50 316 Quantum numbers and energies of
ortho-H2O rotational states
--------------------------------------------------------------------------------
Acknowledgements:
Dmitri Babikov, dmitri.babikov(at)mu.edu
(End) Dmitri Babikov [Marquette University], Patricia Vannier [CDS] 04-Sep-2023