| This thesis focuses on investigations of the photochemistry and FTIR spectroscopy of molecules isolated in low temperature solid parahydrogen. The first project is on the photodissociation of N-methylformamide. The 193 nm UV photolysis of N-methylformamide (HCONHCH3) at 1.9 K in solid parahydrogen produces primary radical fragments ·HCO, ·NHCH 3, ·CONHCH3, and molecules CO and NH2CH 3. It is found that these fragments are formed by dissociation of N-methylformamide along three different competing channels, and the main channel is the rupture of the amide C-N bond. The ·NHCH3 and ·CONHCH 3 radicals are spectroscopically characterized for the first time with the aid of ab initio calculations.;The second project is on FTIR spectroscopic studies of the nuclear spin conversion of ammonia molecules in solid parahydrogen. With rapid freezing in solid parahydrogen, it is possible to trap non-equilibrium nuclear spin populations of ammonia and study the kinetics of equilibration using FTIR spectroscopy. This observation indicates the conversion of para ammonia to ortho ammonia, which is only possible through the flip of nuclear spin. The concentration change of ortho-para ammonia after deposition can be explained as the rotational state population redistribution process after the temperature of the system is changed rapidly from room temperature to 1.8 K. Since the rotational state is coupled to nuclear spin state, which can change slowly, it is possible to monitor the ortho-para concentration change process using conventional FTIR spectroscopy. |
