K. M. McHugh

Photoelectron spectra of the alkali metal cluster anions: Na−n=2−5, K−n=2−7, Rb−n=2−3, and Cs−n=2−3

Obtention des spectres de photoelectrons a 2,540 eV sur faisceaux supersoniques. Deduction des energies de detachement vertical et des affinites electroniques adiabatiques, dont on analyse les variations avec n

Photoelectron spectroscopy of the negative ion SeO

We have recorded the photoelectron spectrum of SeO− using a newly constructed negative ion photoelectron spectrometer. The adiabatic electron affinity of SeO is determined to be 1.456±0.020 eV. Values of ν00(a 1Δ–X 3Σ−0+) and ΔG1/2(a 1Δ) are found to be 5530±200 and 916±35 cm−1, respectively, in substantial accord with previous measurements. The negative ion parameters determined in this work are: B‘e(SeO−) =0.4246±0.0050 cm−1 which leads to  r’e(SeO−)=1.726±0.010 A, ω‘e(SeO−)=730±25 cm−1, ω’e x‘e(SeO−)=2±4 cm−1, and  D0(SeO−)=3.84±0.09 eV. In addition, the spectroscopic parameters of SeO− are compared with those of the electronically analogous negative ions: O−2, SO−, and S−2.

Negative ion photoelectron spectroscopy of the negative cluster ion H−(NH3)1

The negative ion photoelectron spectrum of the negative cluster ion H− (NH3)1 has been recorded with 2.540 eV photons. This negative cluster ion was prepared in a supersonic nozzle‐ion source involving the injection of electrons into an expanding jet. While the spectrum is dominated by a broadened peak centered at 1.430±0.019 eV, there is also a small feature centered at 0.997±0.031 eV. Our interpretation of this spectrum is that the main peak contains the origin of the photodetachment transition, and that the smaller one is due primarily to the excitation of a stretching mode in the ammonia solvent during photodetachment. An upper limit to the dissociation energy of H−(NH3)1 into H− and NH3 is found to be 0.36 eV. This result is in good agreement with calculations by Kalcher, Squires, and Schleyer. The separation between the main and the small peaks is 3490±130 cm−1, and the symmetric stretching frequency of free NH3 is 3506 cm−1. The small peak also shifts appropriately upon deuteration in support of th...

Photoelectron spectroscopy of the negative cluster ions NO−(N2O)n=1,2

We have recorded the photoelectron (photodetachment) spectra of the gas‐phase negative cluster ions NO−(N2 O)1 and NO−(N2 O)2 using 2.540 eV photons. Both spectra exhibit structured photoelectron spectral patterns which strongly resemble that of free NO−, but which are shifted to successively lower electron kinetic energies with their individual peaks broadened. Each of these spectra is interpreted in terms of a largely intact NO−subion which is solvated and stabilized by nitrous oxide. For both NO−(N2 O)1 and NO−(N2 O)2, the ion–solvent dissociation energies for the loss of single N2 O solvent molecules were determined to be ∼0.2 eV. Electron affinities were also determined and found to increase with cluster size. The localization of the cluster ion’s excess negative charge onto its nitric oxide rather than its nitrous oxide subunit is discussed in terms of kinetic factors and a possible barrier between the two forms of the solvated ion.

Negative ion photoelectron spectroscopy of N2O− and (N2O)−2

Abstract We have recorded the photoelectron spectra of the gas phase negative ions N 2 O − and (N 2 O) 2 − both of which were prepared in a nozzle ion source. The shift between the maxima of the two spectra is interpreted in terms of the dissociation energy of the dimer ion.

Negative ion photoelectron spectroscopy of P2

Address of Investigators: Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218.

Photodetachment spectroscopy of cluster anions. Photoelectron spectroscopy of H–(NH3)1, H–(NH3)2 and the tetrahedral isomer of NH–4

The dominant peaks in the photoelectron spectra of the gas-phase, negative cluster ions H–(NH3)1 and H–(NH3)2 provide evidence for describing them as ion-molecule complexes comprised of intact hydride ions which are solvated by ammonia. Vertical detachment energies ad approximate ion–single-solvent dissociation energies are obtained. Other spectral features reveal the complexation-induced distrotion of the ammonia solvent(s) by their hydride sub-ions. In the photoelectron spectra of H–(NH3)1 and additional peak appears which is small and unusually narrow and which does not shift upon deuteration. Evidence is presented for interpreting this peak as arising due to the photodetachment of a tetrahedral isomer of NH–4. This previously unknown ammonium anion is not a cluster species, and it is described as a NH+4 ion core with two Rydberg-like electrons.

The smoke ion source: a device for the generation of cluster ions via inert gas condensation

We report the development of an ion source for generating intense, continuous beams of both positive and negative cluster ions. This device is the result of the marriage of the inert gas condensation method with techniques for injecting electrons directly into expanding jets. In the preliminary studies described here, we have observed cluster ion size distributions ranging fromn=1−400 for Pbn+ and Pbn−, and fromn=12−5700 for Lin−.

Negative ion photoelectron spectroscopy of the heteronuclear alkali-metal dimer and trimer anions : NaK-, KRb-, RbCs-, KCs-, Na2K-, and K2Cs-

Abstract Negative ion photoelectron spectra are reported for the heteronuclear alkali dimer and trimer anions, NaK − , KRb − , KCs − , RbCs − , Na 2 K − , and K 2 Cs − at 488 nm. In addition to assigning all of the electronic transitions observed in the mixed dimer anion spectra, vertical detachment energies, adiabatic electron affinities, and dimer anion dissociation energies have also been determined. A linear correlation between mixed dimer EA a s and α M* / r 2 M*M (α M* = the more electropositive alkali atoms polarizability) confirms the presence of ionic character in heteronuclear alkali dimers. Also, vertical detachment energies and adiabatic electron affinities are reported for the trimer systems.

Negative ion photoelectron spectroscopy of TeH

Substantial spectroscopic data are available about the TeO molecule [l-9]. TeO appears to have first been observed in 1938 by Shin-Piaw in emission spectra [2]. Subsequent spectroscopic work has included emission studies in the visible and in the near-ultraviolet [3-51, absorption in the near-ultraviolet [6], matrix-isolation studies in the infrared [7], and chemiluminescence in the near-infrared [8]. TeO is distinguished from other group VIB diatomic oxides by its unusually large spin-spin splitting in the ground state [8,10]. Thermochemical data on TeO are also available [ 1 l-l 31. In contrast to TeO, very little information is available about its negative ion, TeO-. We are aware of only one observation of TeO. This was by Constantinescu et al. who observed its ESR signal [14]. Here, we report the recording of the photodetachment spectrum of TeOby negative ion photoelectron spectroscopy. We obtain a highly structured spectrum for TeOfrom which the adiabatic electron affinity of TeO and the spectroscopic parameters Bl and 0: for TeOare determined. Using these data, we also calculate r: and Do for TeO.