finding the resonance frequency of substances is apparently a VERY VERY difficult
It depends on molecule structure. More complex substance, more oscillation axis, more resonant frequencies. So, most substances have many resonant frequencies, not one, and it is more common to talk about "vibrational spectrum", instead of "resonant frequency". So, use "vibrational spectrum of ..." to find what you want.
"Resonant frequency" is rarely used in literature like that. What you want is microwave spectroscopic data and the peaks shown in the spectrum are the resonant frequencies
You could probably speed this up by examining harmonic bands then narrowing in on bands where you observe small changes in temp
It depends on molecule structure. More complex substance, more oscillation axis, more resonant frequencies. So, most substances have many resonant frequencies, not one, and it is more common to talk about "vibrational spectrum", instead of "resonant frequency". So, use "vibrational spectrum of ..." to find what you want.
"Resonant frequency" is rarely used in literature like that. What you want is microwave spectroscopic data and the peaks shown in the spectrum are the resonant frequencies