Stable and metastable states of SN⁻

Abstract

Highly correlated ab initio methods were used in order to generate the potential energy functions (PEFs) of the bound electronic states of the SN− anion and the long-range parts of the PEFs of its excited states and their mutual spin–orbit couplings. The SN (X2Π and a4Π) potential energy curves are also computed. In addition to the two bound electronic states of SN− (i.e. X3Σ− and 1Δ) already known, our calculations show that the 3Δ state is lying energetically below its quartet parent neutral state (a4Π). The depletion of the J = 3 component of SN−(3Δ) will mainly occur via weak interactions with the electron continuum wave. At large internuclear distances, SN−(5Π) state is predicted to possess a shallow polarization minimum supporting long-lived SN− ions. Finally, the reaction between S−(2Pu) and N(4Su) involves the electronic states of SN− and their mutual couplings, in competition with the autodetachment processes.

Ab initio characterization of electronically excited metastable states of S2 -

“…In Figure 1 there are depicted the MRCI + Q PEC for all 24 electronic states of S 2 − (thin lines) correlating to the bound asymptote S − ( 2 P u ) + S( 3 P g ), together with those of the neutral S 2 [14] and complete this previous theoretical work. All the S 2 − electronic states are bound at large internuclear distances since they are located below their respective parent states.…”

“…The situation, however, is quite different in the molecular region, and these electronic states should be considered one by one. Here we are presenting only the bound parts of our anionic potentials, since our approach is not valid to describe accurately the negative ion resonances above the autodetachment threshold [1][2][3]. We noticed that our initially computed PECs for S 2 − were shifted to lower energies (by 0.23 eV) in order to match the experimental electron affinity of S 2 (X 3 g − ) [5,6].…”

“…The vibrational structure of S 2 − (X 2 g ) trapped in solid matrices has been also characterized by using Raman spectroscopy [8]. The optically-allowed X 2 g ← A 2 u emission (at ∼20000 cm −1 for the 0-0 transition) has been observed for S 2 − the ions doped in alkali iodides, chlorides, and bromides after laser excitation [9,10]. The lifetime of the emitting A 2 u rovibrational levels are probably lengthened in matrices since the expected gas phase rapid nonradiative autodetachment of the J = 1/2 and J = 3/2 fine components of the A 2 u state to their corresponding X state counterparts is quenched there.…”

“…Recently, metastable negative ions, such as SN − and CS − , have been predicted to exist in electronic states having high-spin multiplicity [1,2,15]. Such high-spin electronic states are good candidates for metastable negative ions.…”

Accurate potential energy function and spectroscopic properties of NS (X²Π) via extrapolation to the complete basis set limit

“…In 1985, Lie et al [28] computed the low-lying valence and Rydberg states of NS employing CI approach. From then on, a number of ab initio calculations [8,28,[29][30][31][32][33][34][35][36][37][38] have been done, in which a series of spectroscopic constants have been confirmed. Very recently, Gao et al [39] studied the spectroscopic properties of the low-lying electronic states of the NS by using ab initio based MRCI+Q+DK method with allelectronic aug-cc-pV5Z basis set.…”