Analysis of the 8f, 9f, and 10f,v=1 Rydberg states ofN2

Abstract

The autoionizing (X X~) gf, 9f, and 10f, v =1 states of N2 have been studied by using doubleresonance ionization spectroscopy via numerous rotational levels of the a 'II~, v'=5 state. These nf states lie in a complex region of the spectrum that also contains transitions to high vibrational levels of the b' 'X"+ valence state and Rydberg states that converge to the X X~, A II",and 8 X"+ states of the ion. A long-range interaction model, which is based on the interaction of the Rydberg electron with the polarizability and quadrupole moment of the N2+ ion core, has been used to intepret the f-state structure and to identify the extent of perturbations due to interactions with nearby states. A generalized least-squares fit of the model to the energies of the unperturbed Sf state yields an effective quadrupole moment of (3.2+0. 1)eao and an isotropic polarizability of (16.1+0.4)ao for the X X~, U+ =1 state of the ion. In addition, a new state that is observed to perturb the 9f, v = 1 state is tentatively identified as the previously unobserved (A H")3dm '6", u =2 state. The results presented here complete the interpretation of the single-photon absorption spectrum of N2 from the first ionization potential at -125 667 to -126 850 cm

Photoelectron angular distributions from rotationally resolved autoionizing states of N2

“…1 that includes the portion containing the (X 2 Σ g + )9f, v = 1 band. The assignments are based on the earlier work of McCormack et al 10,12 This band is very weak relative to most of the other bands, as seen in Fig. 1.…”

“…Figure 1 also includes bands corresponding to transitions to the b 1 Σ u + , v = 42-44 states, the (B 2 Σ u + )3sσ g , v = 0 state, an unassigned 1 Σ u + or 1 Π u state most likely having an A 2 Π u core, and the (X 2 Σ g + )9f, v = 1 state. [4][5][6][7][8][9][10][11][12] The latter is best described in Hund's case (d) 12,13 and is discussed in more detail later on. All of the former bands can be treated at least tentatively in Hund's case (a) or (b).…”

“…12 Thus, Eq. (7) will not adequately describe the rotational branching fractions and rotationally averaged β values for autoionization of this state.…”

“…There is substantial agreement over the assignment of most of the sharp structure, and the lower energy tower has been assigned to a transition associated with the (B 2 Σ u + )3sσ, v = 0 final state; however, despite numerous theoretical 4,9,14,15 and experimental studies, no consensus has been reached for the assignment of the higher energy tower. These previous experiments include extremely high-resolution single-photon absorption and ionization of jetcooled N 2 , 5,16 photoionization from vibrationally excited levels of the neutral electronic ground state, 1 double-resonance studies via the a 1 Π g state, [10][11][12] and comprehensive studies using isotopic substitution. 17 In principle, photoelectron angular distributions can provide insight into the photoionization dynamics and the electronic character of the autoionizing resonances and ejected photoelectron.…”

“…[1][2][3][4][5][6][7] This relatively large number of states can lead to complex resonance features that are perturbed with respect to intensities, linewidths, and expected level positions. Thus, while considerable progress has been made in the analysis of this region of the N 2 spectrum, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] some strong features still lack definitive spectral assignments. Perhaps the most noteworthy of these regions lies between ∼126 200 and 126 500 cm 1 in the single-photon ionization spectrum.…”