#------------Part of unpublished work (to be submitted very soon).
#------------Only partial code is provided.
#------------Need dipole moment and polarizability values.
#------------Information about ion (H3O+, NH4+, NO+ and O2+) required.
#------------Such as temperature inside dridt tube, buffer gas etc.
========================================================================================================================================
This code is a part of series of codes written for the calculations of rate coefficients
of ion-molecule reactions occuring in chemical ionization mass spectrometry (CIMS), typically PTR-MS and SIFT-MS. For the calculation of rate coefficents, 
we need to compute many other prerequisites. This will include the following:

1. Ion kinetic energy in the drift tube chamber (Wannier 1953).

2. Effective drift tube temperature ().

3. Center-of-mass kinetic energy (McFarland 1973).

4. Rates from capture collision models, such as Langevin rates, average dipole orientation (ADO) theory (Su et al. 1973).

5. Classical trajectory and parametrized trajectory method (Su and Chesnavich 1982, 1994).

===========================================================================================================================================

Why you need this calculation?

Rate coefficients for ion-molecule reactions in CIMS are important for the identification and quantification of trace gases (volatile compounds)
present in atmosphere, food products, and many other sources. These reactions occur at zero activation energy and experimental rates are generally a source of
large errors. Aslo, volatile compounds can be identified without instrument calibration if rate coeffcient of the reaction is known. The capture collision models
discussed above are used to approximate these collisions in CIMS.


Applications: Atmospheric science, food and quality control, biology, and medical science.  

References: Ellis et al. 2014, Fuji 2015, Harrison 1992.