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New in Version 2022 (April 2022)

1. MULTIWELL: Enhancement: The master equation code has been restructured in order to take better advantage of the available computer memory with no sacrifice in the other capabilities of the code. As a result, the 2022 version compiles more easily for the Windows platform and can in principle accommodate models containing hundreds of wells and hundreds of reaction channels per well, depending on available computer memory. Thanks to the assistance of Keith Kuwata and Connor Martin, the code ran with no problems using a mechanism consisting of 28 wells, 71 transition states, and up to 4 reaction channels per well. Tests using larger models are welcome!

2. MULTIWELL: Enhancement: Minor revisions were made to the master equation code to facilitate running simulations with larger numbers of stochastic trials. The code was tested successfully with 10^9 stochastic trials. The larger number of trials enables greater dynamic range and reduced stochastic noise, but at the cost of more computer time. (In our experience, most simulations require ≤10^7 stochastic trials.)

3. New example for the MULTIWELL master equation code: “photophyschem” is an implementation of the photophysics and photochemistry of gas phase Acetone [Barker, J. R. New light on acetone: a master equation model for gas phase photophysics and photochemistry. Mol. Phys. 2021, 119, e1958018; DOI: 10.1080/00268976.2021.1958018]. This example illustrates the use of several features of the code, including the optional use of external microcanonical rate constant files (with .rke suffix) and competing unimolecular and bimolecular processes, which are implemented in MULTIWELL by using Kinetic Monte Carlo methods (the MORERXN user option). A method for implementing photoexcitation of thermal population distributions to electronically excited states is also described. This model has successfully simulated both thermal quantum yield measurements in collisional environments at T > 300 K, as well as monochromatic excitation in molecular beams at 10 K.

4. Other revisions: The MultiWell User Manual has been updated and several of the codes have been slightly revised to eliminate minor bugs and to make minor improvements.