Vibrational Spectroscopy of the Dehydrogenated Uracil Radical by Autodetachment of Dipole‐Bound Excited States of Cold Anions

Abstract

Molecules with large enough dipole moments can bind an electron by the dipole field, which has little effect on the molecular core. A molecular anion can be excited to a dipole-bound state, which can autodetach by vibronic coupling. Autodetachment spectroscopy of a complex anion cooled in a cryogenic ion trap is reported. Vibrational spectroscopy of the dehydrogenated uracil radical is obtained by a dipole-bound state with partial rotational resolution. Fundamental frequencies for 21 vibrational modes of the uracil radical are reported. The electron affinity of the uracil radical is measured accurately to be 3.4810±0.0006 eV and the binding energy of the dipole-bound state is measured to be 146±5 cm(-1). The rotational temperature of the trapped uracil anion is evaluated to be 35 K.

Communication: Observation of dipole-bound state and high-resolution photoelectron imaging of cold acetate anions

“…This is the main character of DBSs of anions observed previously. 36,39 Hence, features 1 and 2 are due to the 14 ′1 0 and 8 ′1 0 vibrational levels, respectively, of the excited DBS of CH 3 COO − , as we expected.…”

“…We expected that transitions to the 14 ′ 0 1 and 8 ′ 0 1 vibrational levels of the DBS should occur near the 14 1 0 and 8 1 0 levels of CH 3 COO•, because the binding energy of the DBS was expected to be small. 36,39 Since the photodetachment spectrum was taken over ∼300-530 cm −1 above the detachment threshold, the overall baseline represents the direct photodetachment from the electronic ground state of CH 3 COO − to that of CH 3 COO•. In addition to the weak direct detachment signals, two peaks were observed and labeled as 1 and 2, which must be due to autodetachment by resonant excitation to an electronic excited state of CH 3 COO − .…”

“…Therefore, we estimated that the actual T rot of the trapped CH 3 COO − anions should be in the range of 20-35 K, which is consistent with the 35 K rotational temperature estimated previously for the trapped deprotonated uracil anions. 39 Fig . 3 shows the resonant PE images and spectra of CH 3 COO − measured at 376.36 and 374.27 nm, when the detachment laser was tuned to the positions of 1 and 2 in Fig.…”

A multi-agent quantum Monte Carlo model for charge transport: Application to organic field-effect transistors

“…9(e)-9(h). Such highly nonFranck-Condon resonant PE spectra are not only valuable 153 to provide accurate measurements of vibrational frequencies for those modes with weak Franck-Condon factors, they are also important in the assignments of the observed vibrational levels of the DBS. In fact, the assignments of the 46 observed autodetachment resonances for [U-H] − were done by measuring the resonant PE spectra in conjunction with calculated frequencies.…”

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

“…11(b) for its structure). 153 The [U-H]· radical has a calculated dipole moment of ∼3.2 D, sufficient to bind an electron to give rise to an excited DBS for the anion. The wave function of the DBS excited state of [U-H] − is shown in Fig.…”