Task 4: ExoCross with HITRAN - Trovemaster/exocross GitHub Wiki

1. Download your transition line list from HITRAN

i. Go to the website hitran.org and register

ii. Once your registration has been successful, go to the ‘Data Access’ tab and select ‘Line-by-line’

iii. Select you desired molecule (e.g. C2H2) and make a note of the molecule number (e.g. 26), then click on ‘2. Select isotopologues’

iv. Make sure only the first isotopologue box is ticked, then make a note of the corresponding AFGL code (e.g. 1221, which we will need later) and click on ‘3. Select wavenumber / wavelength range’

v. Leave vmax as blank, and vmin as zero, and move on to ‘4. Select output options’

vi. Click on ‘5. Start Data Search’

vii. Download the .par file and save to a new folder (e.g. /scratch/dp114/yourusername/HITRAN)

2. Calculate absorption cross-sections

i. Move to your HITRAN directory.

ii. Now we need to find the partition function for your molecule. Type tipps.exe in the command line to run the tipps (total internal partition sum) executable and follow the prompts. When you are told to choose an isotopologue, type in the AFGL code you noted earlier. Select your desired temperature and make a note of the partition function Q(T). Note: tipps will automatically return to step 1 after it’s displayed Q(T), so press ctrl+c to exit the program.

iii. Create an input file as shown bellow (C2H2.inp)

    Temperature  400
    Range 0 8000.0
    
    Npoints 80001
    
    iso 261
    
    HITRAN
    
    absorption
    Doppler
    mass 26
    
    pf 6.993989E+02
    output C2H2_T300K_Doppl_0.1_HITRAN
    Transitions  5c4bb92c.par

Modify the file as you wish but remember, your ‘iso’, ‘pf’ and ‘temperature’ input must match your selections thus far. Your ‘Transitions’ input should be the .par file that you downloaded in section 1: type ls (list) into the command line to view all the files in your current directory.

vi. Finally we can calculate the absorption cross-sections for your molecule at your chosen temperature by typing

exocross.exe < C2H2.inp

in the command line to launch the exocrossexecutable with C2H2.inp as an input.

##3. Plot your cross-sections

To plot your calculated cross-sections using the program xmgrace type xmgrace your_xcross_output.xsec and play around!

Useful Linux commands

• cd /full/path/to/directory – change current directory to /full/path/to/directory
• cd directory – move into the folder directory which is located in your current directory
• cd .. – move to parent directory e.g move from /full/path/to/directory to /full/path/to
• pwd – show present working directory
• ls – list all files and directories in current directory
• cp /full/path/to/fileA /full/path/to/fileB – copy fileA to fileB
• cp fileA fileB – copy fileA in your current directory to fileB also in your current directory
• more file – show contents of file