Role of Polarization Interactions in the Formation of Dipole-Bound States.

Even though there is a critical dipole moment required to support a dipole-bound state (DBS), how molecular polarizability may influence the formation of DBSs is not well understood. Pyrrolide, indolide, and carbazolide provide an ideal set of anions to systematically examine the role of polarization interactions in the formation of DBSs. Here, we report an investigation of carbazolide using cryogenic photodetachment spectroscopy and high-resolution photoelectron spectroscopy (PES).

Resonant two-photon photoelectron imaging and adiabatic detachment processes from bound vibrational levels of dipole-bound states.

Anions cannot have Rydberg states, but anions with polar neutral cores can support highly diffuse dipole-bound states (DBSs) as a class of interesting electronically excited states below the electron detachment threshold. The binding energies of DBSs are extremely small, ranging from a few to few hundred wavenumbers and generally cannot support bound vibrational levels below the detachment threshold. Thus, vibrational excitations in the DBS are usually above the electron detachment threshold and they have been used to conduct resonant photoelectron spectroscopy, which is dominated by state-specific autodetachment.

Observation of a dipole-bound excited state in 4-ethynylphenoxide and comparison with the quadrupole-bound excited state in the isoelectronic 4-cyanophenoxide.

Negative ions do not possess Rydberg states but can have Rydberg-like nonvalence excited states near the electron detachment threshold, including dipole-bound states (DBSs) and quadrupole-bound states (QBSs). While DBSs have been studied extensively, quadrupole-bound excited states have been more rarely observed. 4-cyanophenoxide (4CP) was the first anion observed to possess a quadrupole-bound exited state 20 cm below its detachment threshold.

Probing the Dipole-Bound State in the 9-Phenanthrolate Anion by Photodetachment Spectroscopy, Resonant Two-Photon Photoelectron Imaging, and Resonant Photoelectron Spectroscopy.

Valence-bound anions with a dipolar core can support dipole-bound states (DBSs) below the electron detachment threshold. The highly diffuse DBS observed is usually of σ symmetry with an s-like orbital. Recently, a π-type DBS was observed experimentally in the 9-anthrolate anion (9AT) and it was shown to be stabilized due to the large anisotropic polarizability of the 9AT core.

Photodetachment spectroscopy and resonant photoelectron imaging of cryogenically cooled 1-pyrenolate.

We report an investigation of the 1-pyrenolate anion (PyO) and the 1-pyrenoxy radical (PyO) using photodetachment spectroscopy and resonant photoelectron imaging of cryogenically cooled anions. The electron affinity of PyO is measured to be 2.4772(4) eV (19 980 ± 3 cm) from high-resolution photoelectron spectroscopy.

Observation of a Symmetry-Forbidden Excited Quadrupole-Bound State.

We report the observation of a symmetry-forbidden excited quadrupole-bound state (QBS) in the tetracyanobenzene anion (TCNB) using both photoelectron and photodetachment spectroscopies of cryogenically-cooled anions. The electron affinity of TCNB is accurately measured as 2.4695 eV.

Polarization of Valence Orbitals by the Intramolecular Electric Field from a Diffuse Dipole-Bound Electron.

The diffuse electron in a dipole-bound state is spatially well separated from the valence electrons and is known to have negligible effects on the dipole-bound state's molecular structure. Here, we show that a dipole-bound state is observed in deprotonated 4-(2-phenylethynyl)-phenoxide anions, 348 cm below the anion's detachment threshold. The photodetachment of the dipole-bound electron is observed to accompany a simultaneous shakeup process in valence orbitals in this aromatic molecular anion.

Observation of a π-Type Dipole-Bound State in Molecular Anions.

We report the observation of a π-type dipole-bound state (π-DBS) in cryogenically cooled deprotonated 9-anthrol molecular anions (9AT^{-}) by resonant two-photon photoelectron imaging. A DBS is observed 191  cm^{-1} (0.0237 eV) below the detachment threshold, and the existence of the π-DBS is revealed by a distinct (s+d)-wave photoelectron angular distribution.

Photodetachment spectroscopy and resonant photoelectron imaging of the 2-naphthoxide anion via dipole-bound excited states.

We report a photodetachment spectroscopy and high-resolution resonant photoelectron imaging study of cryogenically cooled 2-naphthoxide anions (CHO). The photodetachment spectrum revealed a dipole-bound state (DBS) 202(4) cm below the detachment threshold and 38 resonances corresponding to the vibrational levels of the DBS. By tuning the detachment laser to these above-threshold resonances, we obtained 38 resonantly enhanced photoelectron spectra, which were highly non-Franck-Condon as a result of mode-selective vibrational autodetachment from the DBS.

Probing the Critical Dipole Moment To Support Excited Dipole-Bound States in Valence-Bound Anions.

We report photodetachment spectroscopy and high-resolution photoelectron imaging of -halogen substituted phenoxide anions, -XCHO (X = F, Cl, Br, I). The dipole moments of the -XCHO neutral radicals increase from 2.56 to 3.

Resonant Two-Photon Photoelectron Imaging and Intersystem Crossing from Excited Dipole-Bound States of Cold Anions.

We report the observation of a dipole-bound state (DBS) 659 cm below the electron detachment threshold of cryogenically cooled deprotonated 4,4'-biphenol anion (bPh) and 19 of its lowest vibrational levels. Resonant two-photon photoelectron imaging (R2P-PEI) via the vibrational levels of the DBS displays a sharp peak with a constant binding energy. This observation indicates vertical detachment from the vibrational levels of the DBS to the corresponding neutral levels with the conservation of the vibrational energy, suggesting that the highly diffuse electron in the DBS has little effect on the neutral core.

Tautomer-Specific Resonant Photoelectron Imaging of Deprotonated Cytosine Anions.

Tautomers of the nucleobases play fundamental roles in spontaneous mutations of DNA. Tautomers of neutral cytosine have been studied in the gas phase, but much less is known about charged species. Here, we report the observation and characterization of three tautomers of deprotonated cytosine anions, [trans-keto-amino-N3H-H8b] (tKAN3H8b ), [cis-keto-amino-N3H-H8a] (cKAN3H8a ) and [keto-amino-H] (KAN1 ), produced by electrospray ionization.

Dipole-bound excited states and resonant photoelectron imaging of phenoxide and thiophenoxide anions.

We report photodetachment and resonant photoelectron-imaging studies of cryogenically cooled phenoxide (CHO) and thiophenoxide (CHS) anions. In a previous study [H. T.

Construction of pH-Sensitive "Submarine" Based on Gold Nanoparticles with Double Insurance for Intracellular pH Mapping, Quantifying of Whole Cells and in Vivo Applications.

A series of "submarines", which composed of gold nanoparticles and modified with rhodamine and fluorescein derivatives, were presented. With dual sensitive units for both acidic and basic environment, these "gold nano-submarines" not only allow efficient intracellular pH mapping but also provide more accurate quantitative detection of pH alteration under different stimuli with distinct pH quantification range. Moreover, they even have the ability to pass through the blood brain barrier (BBB).