N 3 + : Full-dimensional ground state potential energy surface, vibrational energy levels, and dynamics

Abstract

The fundamental vibrational frequencies and higher vibrationally excited states for the N3+ ion in its electronic ground state have been determined from quantum bound state calculations on three-dimensional potential energy surfaces (PESs) computed at the coupled-cluster singles and doubles with perturbative triples [CCSD(T)]-F12b/aug-cc-pVTZ-f12 and multireference configuration interaction singles and doubles with quadruples (MRCISD+Q)/aug-cc-pVTZ levels of theory. The vibrational fundamental frequencies are 1130 cm−1 (ν1, symmetric stretch), 807 cm−1 (ν3, asymmetric stretch), and 406 cm−1 (ν2, bend) on the higher-quality CCSD(T)-F12b surface. Bound state calculations based on even higher level PESs [CCSD(T)-F12b/aug-cc-pVQZ-f12 and MRCISD+Q-F12b/aug-cc-pVTZ-f12] confirm the symmetric stretch fundamental frequency as ∼1130 cm−1. This compares with an estimated frequency from experiment at 1170 cm−1 and previous calculations [Chambaud et al., Chem. Phys. Lett. 231, 9–12 (1994)] at 1190 cm−1. The remaining disagreement with the experimental frequency is attributed to uncertainties associated with the widths and positions of the experimental photoelectron peaks. Analysis of the reference complete active space self-consistent field wave function for the MRCISD+Q calculations provides deeper insight into the shape of the PES and lends support for the reliability of the Hartree–Fock reference wave function for the coupled cluster calculations. According to this, N3+ has a mainly single reference character in all low-energy regions of its electronic ground state (3A″) PES.

Time-dependent quantum mechanical wave packet dynamics

“…They found a slightly larger number of bound states than what was reported by Lee and Secrest earlier. 191 Very recently, Koner et al 192 have computed the bound states of N 3 + in three dimensions, for J = 0, using the TDQMWP method on a newly computed ab initio PES and found that the resulting lowest 20 bound states were in excellent agreement with those obtained using the TIQM method and DVR3D code available. 193…”

Chemical versatility of azide radical: journey from a transient species to synthetic accessibility in organic transformations

“…The rovibronic spectrum (X ˜3S À g -A ˜3P u ) analysis provided information about the electronic GS of N 3 + , a linear and centrosymmetric (D Nh ), with an N-N bond length of 1.193 Å. [24][25][26] The GS term of the N 3 + ion is X ˜3S À g , and the first ionization potential (IP) of N 3 with the 2 P g ground state is (11.06 AE 0.01) eV, which was directly measured from the photoelectron spectrum (PES) by A. Morris et al 11 The systems N 3 + (A ˜3P u , 1 1 P u ) and N 3 (X ˜2P g ) are the type-A…”

Photodissociation dynamics of N$_{3}^{+}$

“…The 1 3 A ground state PES, correlating with the 3 Σ − g state in linear geometry and dissociating to N + ( 3 P)+N 2 (X 1 Σ + g ), was already discussed in earlier work. 13 Next up in energy are the 1 A and 1 A states (see left panel in Figure 1), which are degenerate for θ = 0, correlate with the 1 ∆ g state and dissociate to N + ( 1 D)+N 2 (X 1 Σ + g ). Upon bending away from the linear structure the degeneracy is lifted and two states -1 A and 1 A -emerge as is shown in Figure 1 middle and right panels.…”

“…However, a full-dimensional PES for the electronic ground state has only become available recently. 13 The construction of high-dimensional PESs is a challenging problem for which machine learning-based approaches like neural networks or kernel-based methods have found wide applicability in recent times. [14][15][16][17] One such method, rooted in the theory of reproducing kernel Hilbert spaces (RKHSs), 18 is suitable for obtaining reliable PESs.…”

“…This method was utilized in previous work for the construction of an accurate PES for the ground state of N + 3 at the multi reference configuration interaction (MRCI) level of theory. 13 A similar methodology has been followed for the construction of high quality PESs for other triatomic species such as the [CNO] system, 19 N − 3 , 20 and NO 2 . 21 In the current work the focus is on those excited states of the N + 3 cation which are expected to be accessible during photoexcitation.…”