The X-2 Sigma(+)(g) and B-2 Sigma(+)(u) states of N-2(+): hyperfine and nuclear quadrupole coupling constants, electric quadrupole moments, and electron-spin g-factors. A theoretical study

摘要

The variation with bond distance of hyperfine coupling constants (lifec) [A(iso), A(dip)], nuclear quadrupole coupling constants (nqcc) [chi], molecular electric quadrupole moments [Theta], and electron-spin g-factors is reported for X(2)Sigma(g)(+)(sigma(2)pi(u)(4)2sigma(g)) and B(2)Sigma(u)(+)(1sigma(u)gpiu(4)(2)sigma(g)(3)) of N-2(+). The hfcc's, nqcc's, and Theta's are studied with ab initio and density functional theory methods. Calculated A(iso)/A(dip) of 91.3/29.7 MHz for the X state have to be compared with experimental values of 102.4/23.3 MHz. For the B state, theoretical values A(iso)/A(dip) = 793/6.8 MHz support an experimental A(iso) = 708 MHz (1sigma(u) is largely s) but disagree with A(dip) = 26 MHz (large p). The nqcc chi(B) is one order of magnitude larger than chi(X), 4.80 versus -0.58 MHz, in line with literature results. Omission of nqcc contributions in the analysis of optical spectra is most probably responsible for the anomalously high "experimental" Adip(B). The quadrupole moment 0 is positive for both X and B states of N-2(+), whereas it is negative for neutral N-2(X). The vibrational absorption 2 intensity for the v = I <-- 0 quadrupole transition of N-2(+)(A) is about six times stronger than for N-2(X). The g(perpendicular to)-shift (Deltag(perpendicular to) = g(perpendicular to) - g(e)) is evaluated with multireference configuration interaction wavefunctions, via second-order sum-over-states expansions. The Deltag()'s are small (approximate to100 ppm), while Deltag(perpendicular to) (v = 0) is -2710 ppm for X(2)Sigma(g)(+) and -6165 ppm for B(2)Sigma(n)(+). Interaction parameters lpha(e), 31.12cm(-1) and beta(el) = 1.01 a.u. calculated for the A(2)Pi(u) similar to B(2)Sigma(u)(+) perturbation are in I me with 31.30 cm(-1) and 1.07 a.u. averaged over five experimental studies. Our Deltagperpendicular to(u)'s are compared with Curl's shifts obtained from experimental spin-rotation (gamma) and rotational constants. Good agreement is found for X but not for the B state, for which it is suggested that experimental - (B, U)'s recently reported-where gamma decreases sharply with vibrational level v-should be revised. (C) 2004 Elsevier Inc. All rights reserved.