Infrared radiative cooling of gas‐phase ions

For the first time orbital mediated tunneling spectroscopy (OMTS) is reported for the same species, vanadyl phthalocyanine (VOPc), in both the tunnel diode and STM environments. IETS and OMTS for a junction of the form [Al−Al2O3−VOPc−Pb] show both the expected bias symmetry of vibrational and electronic inelastic electron tunneling spectroscopy (IETS) bands and the highly bias asymmetric OMTS band associated with tunneling via direct occupation of the Pc ring π* orbital. STM studies of submonolayer coverage of VOPc on Au(111) produce well-resolved submolecular images of the molecule. Current imaging tunneling spectroscopy (CITS) allows one to easily identify VOPc islands, and the resulting I−V curves can be used to generate dI/dV spectra for VOPc and for bare gold regions. An intense band seen near +1.4 V bias (Au+) is identified as the same OMTS band as seen in the tunnel diode:  resonance-like tunneling through the Pc ring π* orbital.

Orbital Mediated Tunneling in Vanadyl Phthalocyanine Observed in both Tunnel Diode and STM Environments

The rate coefficient for the dissociative recombination of HCO+ has been measured using a new flowing afterglow technique which employs a movable Langmuir probe to measure electron density and a movable mass spectrometer to measure ion density, both as a function of distance along the flow. A value of 2.2×10−7 cm3 s−1 has been found at 300 K. An analysis of the excitation state of the ions indicates that more than 93% are in the v=0 state while the rest have ∼0.1 eV of internal energy. A discussion of recent theoretical controversy concerning this ion is given.

A further study of HCO+ dissociative recombination

The technique of direct laser absorption spectroscopy in fast ion beams has been employed for the determination of absolute integrated band intensities (S0v) for the ν3 fundamental bands of H3O+ and NH+4. In addition, the absolute band intensities for the ν1 fundamental bands of HN+2 and HCO+ have been remeasured. The values obtained in units of cm−2 atm−1 at STP are 1880(290) and 580(90) for the ν1 fundamentals of HN+2 and HCO+, respectively; and 4000(800) and 1220(190) for the ν3 fundamentals of H3O+ and NH+4, respectively. Comparisons with ab initio results are presented.

Absolute infrared vibrational band intensities of molecular ions determined by direct laser absorption spectroscopy in fast ion beams

A variety of high-quality spectroscopic studies have contributed to knowledge of the formyl cation, HCO+, and its rare isotopologues, but technical limitations have previously limited precise determinations of the far-infrared, or terahertz spectrum. This study extends the microwave, millimeter, and submillimeter spectroscopy of HCO+ into the terahertz range. The resulting measurements and predictions are of sufficient coverage to adequately address astrophysical questions about this species using the Herschel Space Observatory or the Atacama Large Millimeter Array.

http://iopscience.iop.org/article/10.1086/517602/pdf

Rotational Spectrum of the Formyl Cation, HCO+, to 1.2 THz

The authors report the determination of absolute integrated band intensities (S{sub v}{sup 0}) for the {nu}{sub 1} fundamental bands of HN{sub 2}{sup +} and HCO{sup +} by the recently developed technique of direct laser absorption spectroscopy in fast ion beams. The values obtained for HN{sub 2}{sup +} (1,250 (300) cm{sup {minus}2} atm{sup {minus}1}) and HCO{sup +} (430 (100) cm{sup {minus}2} atm{sup {minus}1}) are substantially lower than corresponding results from high level ab initio calculations.

Absolute IR intensities of the .nu.1 bands of hydrodinitrogen(1+) and oxomethylium determined by direct laser absorption spectroscopy in fast ion beams

E. R. Keim

Papers

Absolute IR intensities of the .nu.1 bands of hydrodinitrogen(1+) and oxomethylium determined by direct laser absorption spectroscopy in fast ion beams