Photodissociation of N₂O. I. Ab Initio Potential Energy Surfaces for the Low-Lying Electronic States X̃ ¹A‘, 2 ¹A‘, and 1 ¹A‘ ‘

Abstract

Adiabatic potential energy surfaces of the three lowest lying singlet states, X 1 A′ 2 1 A′, and 1 1 A′′, of N 2 O have been computed as a function of the R N 2 -O bond distance and the Jacobi angle. The calculations are performed using the complete-active-space self-consistent field (CASSCF) and the multireference configuration interaction (MRCI) electronic structure methods. It is shown that there is a wide avoided crossing between the ground, X 1 A′, and lowest excited, 2 1 A′, electronic state. This avoided crossing is thought to give rise to a seam of conical intersection at other N-N separations. Both excited state surfaces display important conical intersections at linear geometries. The transition dipole moment surfaces for the two excitation processes (2 1 A′ r X 1 A′ and 1 1 A′′ r X 1 A′) are also presented. These calculations provide the basic data needed to compute the dynamics of the N 2 O + hν f N 2 + O( 1 D) photodissociation process for photon frequencies in the range 5.2 eV (240 nm) to 7.3 eV (170 nm).

Photodissociation of N2O: Energy partitioning

“…7 Two-dimensional PESs for several singlet and triplet states of linear N 2 O were calculated by Hopper. 4 Brown et al 15 and Daud et al 16 constructed two-dimensional PESs for several low-lying singlet states. Because dissociation at 204 nmat the onset of the absorption spectrum-showed very weak vibrational excitation of N 2 , 9 the NN bond length, which changes by only 1% from N 2 O to O + NN, was fixed at the X-state equilibrium value in these studies.…”

“…PESs including all three internal degrees of freedom were calculated by Nanbu and Johnson 17 for the two lowest 1 A states. The PESs of Brown et al, 15 Daud et al, 16 and Nanbu and Johnson 17 were used in wave packet calculations in order to unravel the dynamics of the UV dissociation of N 2 O. [16][17][18] Although these calculations were helpful in understanding the main aspects of the fragmentation, the comparison with the experimental data was not convincing, and several facets remained unexplained, including the origin of the diffuse vibrational structures.…”

Preparation of Novel Polyazetes

“…120 Numerous structure and force field calculations reported for nitrous oxide [89][90][91][92][93][94][121][122][123][124][125][126][127] have shown that obtaining reliable results for both geometry and vibrational frequencies requires an extensive treatment of electron correlation and large basis sets. Our calculated values for N-N and N-0 distances, 1.121 Ä and 1.184 Ä, respectively, are in excellent agreement with the experimental values of 1.127 Ä and 1.185 A.…”

Single-field slice-imaging with a movable repeller: Photodissociation of N2O from a hot nozzle

“…In recent years N 2 O has been subject to a number of high resolution experiments [13][14][15][16] using VMI, [17][18][19][20][21][22] as well as high level theoretical calculations. [23][24][25][26][27][28][29][30][31][32] In the most recent VMI study of Suzuki and coworkers, 22 the authors ionized individual rotational states of the N 2 photoproduct. Velocity map images showed three distinct velocities, corresponding to photodissociation of the three lowest vibrational states (0, v 2 ≤ 2, 0) of N 2 O, which were populated in the molecular beam expansion.…”