Fig. 3: Time constants of collisional dissipation of N2O.
From: Observing collisions beyond the secular approximation limit
The blue circles with error bars (representing two standard deviations of the mean) are the density-normalized decay time constants τE of the echoes deduced from the measurements of the alignment signal recorded at various N2O(4%) + He(96%) gas densities and fixed delays τ12 between the two pulses. The dashed lines denote the results of simulations conducted by solving the density matrix equations for molecules impulsively aligned by two short laser pulses and interacting with each other through collisions. The green and black dashed lines have been obtained using the standard Bloch equations (i.e., using the secular approximation) with initial N2O rotational populations corresponding to temperatures of T = 100 K and 295 K, respectively. The red dashed line represents the results obtained, for populations associated with T = 100 K (see text), using the nonsecular Redfield equations, i.e. including all relaxation terms in Eq. (3).
