Ultrashort-Lived Non-Rydberg Doubly Excited Resonances Observed in Molecular Photoionization

Abstract

The N2 1sB 2 Xd dispersed fluorescence from photon excited N2 molecules has been measured in the 19–34 eV excitation range, where our theory predicts the existence of non-Rydberg doubly excited resonances which autoionize in the sub-fs regime into the N2 1 B2S1u ionic state. The experimentally deduced vibrational branching ratios sy0 ­ 1dysy0 ­ 0d revealed five prominent features, four of which could be identified as such doubly excited resonances based on the lowest order of the many-body perturbation theory. [S0031-9007(96)00230-X]<p>NR</p

Characterisation of a new VUV beamline at the Daresbury SRS using a dispersed fluorescence apparatus incorporating CCD detection

“…At photon energies greater than the v' = 1 threshold, the (1,0) and (1,2) bands also become apparent in the dispersed fluorescence spectra [13]. This effect has been observed in previous synchrotron radiation studies [12,14].…”

The and states of N2+: hyperfine and nuclear quadrupole coupling constants, electric quadrupole moments, and electron-spin g-factors. A theoretical study

“…Higher-lying states were studied [7,8,[24][25][26] to rationalize high-energy ionization spectra of N 2 [5,6,[27][28][29][30][31][32][33][34]. Surprisingly, very little has been done theoretically regarding the ''hyperfine'' N þ 2 parameters (A iso , A dip , v, and c I ), with the exception of a CASSCF/MRCI study on the nuclear quadrupole coupling constants (nqcc) vÕs for the X, A, and B states [35].…”

Evidence for a non-Rydberg molecular doubly excited state of Ca2

“…If we now consider actual electron configuration double excitations (not involving fine structure), a number of examples reported so far were concerned with quite large double excitation energies and the coupling used for spectroscopic purposes involved an autoionization channel. For instance, doubly excited states of molecules H 2 , N 2 and CO show up as resonances in their photoionization spectra [4,5,6]. In the context of ultracold collisions, doubly excited states of the Na 2 molecule link the association reaction between two Na(3p 2 P) atoms to the associative ionization forming Na + 2 [7,8].…”