作者:Colan Linton、Benoit Simard、Hans Peter Loock、Sara Wallin、Gretchen K. Rothschopf、Robert F. Gunion、Michael D. Morse、Peter B. Armentrout
DOI:10.1063/1.479759
日期:1999.9.15
A spectroscopic study of the Rydberg states of YO accessed from particular rotational levels of the A 2Π1/2, v=0 state has been combined with a pulsed field ionization, zero electron kinetic energy (PFI-ZEKE) investigation. The results provide accurate values of the ionization energy of YO, ionization energy I.E.(YO)=49 304.316(31) cm−1 [6.112 958(4) eV], and of the rotational constant (and bond length) of the YO+ cation in its X 1Σ+, v=0 ground state, B0+=0.4078(3) cm−1 [r0=1.7463(6) Å]. The improved value of I.E.(YO) combined with the known ionization energy of atomic yttrium then leads to the result D00(Y−O)−D00(Y−O)=0.1041±0.0001 eV. Combining this result with the value of D00(Y+−O) obtained from guided ion beam mass spectrometry yields an improved value of D00(Y−O)=7.14±0.18 eV. The PFI-ZEKE spectra display an interesting channel-coupling effect so that all rotational levels with J+⩽J′(A)+0.5 are observed with high intensity, where J+ is the angular momentum of the YO+ cation that is produced and J′(A) is the angular momentum of the A 2Π1/2 state that is reached when the first photon is absorbed. This is thought to result from the interaction between the dipole moment of the rotating YO+ core and the Rydberg electron, which can induce changes in l and J+ subject to the dipolar coupling matrix element selection rule, ΔJ+=±1, Δl=±1. The channel-coupling mechanism also appears to induce an inverse autoionization process in which an unbound electron with a low value of l is captured either by its low-J+ YO+ cation or by a second YO+ cation with the same value of J+. This inverse autoionization process is extremely sensitive to the electron kinetic energy, leading to narrow peaks in the PFI-ZEKE spectrum which are only slightly broader than the laser linewidth employed for this study (0.25 cm−1).