Iam trying to measure the degree of converaion of light cured and dual cured resin composites using an FTIR with ATR accessory with the following parameters [128 scan rate , resolution of 4 cm^-1]

However the resulted apectrum has no peak at 1638 cm^-1

I tried to increase the scan rate however it did not worked

Please If anyone faced the same issued and solved the problem to tell me the solution 🙏