Quantum theory Grassmann algebra Path integral Two-level systems Approximation theory Electron energy levels Perturbation techniques Spin models Variance squeezing Calculations Dissociation Indirect photodissociation processes Ising model Photochemical reactions Three dimensional Three dimensional infinite order sudden quantum theory Entanglement Normal squeezing Photons Squeezed Triatomic photodissociation Two-mode interaction Cavity fields Computation theory Dyson equation Entropy squeezing Harmonic generation Information entropy Integral equations Mathematical models