Lots of them. I wrote 6 on my way to my Ph.D. in the late 1990s, and there was plenty of prior art at that time. Here's one of mine, see references therein as

Lots of them. I wrote 6 on my way to my Ph.D. in the late 1990s, and there was plenty of prior art at that time. Here's one of mine, see references therein as well: https://pubs.aip.org/aip/jcp/article-abstract/110/7/3326/475549/Quantum-dynamics-of-overtone-relaxation-in-30-mode https://pubs.aip.org/aip/jcp/article-abstract/110/7/3326/475...