D. M. Lindsay

Raman spectra of mass‐selected cobalt dimers in argon matrices

The absorption and Raman spectra for nickel dimers in an argon matrix prepared by the mass‐selected ion deposition technique have been measured. A weak dimer absorption band is centered around 480 nm. Resonance Raman spectra obtained from exciting into the dimer 480 nm band show a vibrational progression for which ωe=259.2±3.0 cm−1 with ωexe=1.9±0.7 cm−1. The dinickel Raman spectra are discussed in terms of isotopic shifts, as well as the changeover from d–d bonding to s–s bonding along the series Fe2→Cu2.

Raman spectra of mass‐selected vanadium dimers in argon matrices

We report the first Raman measurements on a matrix sample prepared by the mass‐selected ion deposition technique. Vanadium dimer ions, produced by sputtering, were mass selected with a Wien filter and codeposited with Ar and electrons. Raman spectra gave ωe″= 536.9(1.1) and ωexe″ = 4.1(0.1) cm−1, in good agreement with previous measurements.

Deposition of mass selected gold clusters in solid krypton

We report on the deposition of size selected gold dimers and trimers in krypton matrices. Gold cluster ions were produced by sputtering, mass selected in a quadrupole mass filter, and then codeposited with krypton on a CaF2 window in the presence of low energy electrons. Neutralized cluster samples were interrogated in situ by excitation and fluorescence spectroscopy. The spectra found for Au2 (absorption bands at 212, 250, 298, and 347 nm) are in reasonable accord with previous measurements made in Ar matrices. For the trimer we find four strong absorption bands centered at 233, 255, 282, and 308 nm, plus three weaker features lying further to the red. The dimer spectra are discussed with reference to gas phase measurements and recent molecular structure calculations.

Resonance Raman spectrum and excitation profile of mass‐selected zirconium trimers

We present the resonance Raman and Raman excitation profile of mass‐selected zirconium trimers in argon matrices. In the Raman spectra, two fundamentals and one overtone are observed. Average Raman shifts, along with standard deviations (in parentheses) are 176.7 (13) cm−1 (ν2), 258.0 (12) cm−1 (ν1), and 516.1 (8) cm−1 (2ν1). The ratio of the frequencies of the two lowest lines (ν1/ν2) is 1.46, which is very close to √2. This is indicative of a symmetrical equilateral geometry (D3h). In such a case we expect two normal frequencies, one for a totally symmetric stretch of symmetry a′1 (ν1) and a doubly degenerate bend of symmetry e′(ν2). The Raman excitation profiles of the ν1(a′1) line shows two broad maxima: one near 491 nm and the other near 614 nm. The ν2 (e′) profile shows a broad region of intensity only near 614 nm. With the aid of theory we assign the 614 nm band to be 1A′1−1E′ (x,y polarized) while the 491 nm band must be 1A′1−1A″2 (z polarized).

Absorption and Raman spectroscopy of mass‐selected tantalum tetramers in argon matrices

We have examined both the absorption and resonance Raman spectra of mass‐selected Ta tetramers. The tetramers are produced in a sputtering source and mass filtered with a Wien filter, then neutralized and deposited in an Ar matrix at low temperatures. The absorption spectrum indicates two broad transitions, one in the red at 768 nm and another to the blue at 532 nm. Raman resonances could be excited in both regions giving three distinct fundamental frequencies at 270.2(1) cm−1, 185.1(1) cm−1, and 130.6(2) cm−1. The lowest vibration shows a long progression (up to seven overtones) with alternating separations of 135 cm−1 and 126 cm−1, indicative of a weak Jahn–Teller effect in the tetramer ground state. This, along with the observation that the fundamental frequency ratios are close to 2:√2:1 indicate that the molecule has a tetrahedral ground state geometry with an electronic E state symmetry. The appearance of three fundamentals in the resonance Raman spectrum indicates that both excited states correspon...

RAMAN SPECTRA OF RUTHENIUM DIMERS

The absorption (scattering depletion) spectrum and resonance Raman spectrum for Ru2 in an argon matrix prepared by the mass-selected ion deposition technique have been obtained. The absorption spectrum in the visible region shows a single broad transition centered at 470 nm. Resonance Raman spectra, obtained by excitation into this band with dye laser radiation, display a single sharp progression with lines at 343.8(26) cm−1, 681.6(32) cm−1, 1017.5(26) cm−1, 1350.2(25)cm−1,and 1678.9(8) cm−1. These data give ωe=347.1±0.9 cm−1 with ωexe=1.85±1.5 cm−1, leading to a spectroscopic dissociation energy of 2.0±0.2 eV. Sidebands in the Raman spectra are indicative of a weak coupling (Huang–Rhys factor, S∼0.1–0.7) between the dimer and the phonons of the argon host.

ABSORPTION, FLUORESCENCE, AND RAMAN SPECTRA OF MASS-SELECTED RHENIUM DIMERS IN ARGON MATRICES

We report absorption, laser fluorescence, and Raman spectra for Re2 in an argon matrix prepared by the mass‐selected ion deposition technique. The dirhenium absorption spectrum consists of seven band systems (A–G) extending from the near infrared into the ultraviolet region. For the A system (a simple vibrational progression), we find T0=10 817(1) cm−1, ωe=317.1(5) cm−1 and ωexe=1.0(1) cm−1. A Franck–Condon analysis of the A system intensities predicts that this state has a smaller equilibrium internuclear distance than the ground state (Δre=−0.073 A), in violation of Badger’s rule. The B system starts at 13 250 cm−1 and consists of four overlapping (and possibly perturbed) subsystems, whose average vibrational spacing is 270(11) cm−1. The C, D, E, and F systems (vibrational spacings in parentheses) are centered at 22 300 cm−1 (210 cm−1), 24 500 cm−1 (195 cm−1), 29 150 cm−1 (175 cm−1), and 32 900 cm−1 (160 cm−1), respectively. Weak fluorescence spectra, obtained upon laser excitation into the A system, we...

Spectroscopy of yttrium dimers in argon matrices

The absorption and resonance Raman spectra of yttrium dimers (Y2) in argon matrices are measured for the first time. The absorption spectrum (scattering depletion spectrum SDS) shows a weak, broad transition centered near 485 nm. Resonance Raman spectra obtained by exciting into this absorption band with several visible laser lines (465.5–496.5 nm) give a single, sharp progression with up to ten Stokes transitions. These data give ωe=184.4(4) cm−1, with ωexe=0.30(3) cm−1, leading to a spectroscopic dissociation energy of De=3.5(4) eV. Comparison of our results with several ab initio calculations adds confirmation to the assignment of the ground state of Y2 to be the 1Σg+ state.

Absorption, resonance Raman, and Raman excitation spectra of hafnium trimers

We report on the optical, resonance Raman, and excitation profile spectra of mass selected hafnium trimers in argon matrices at 14 K. The absorption spectrum consists of four overlapping transitions in the range 605–620 nm. The Raman spectrum is too complex to be attributed to a single ground state. We may explain the observed spectrum by assuming five low-lying excited states A, B, C, D, and E at 319.0, 413.4, 609.6, 642.8 (weak), and 785.4 cm−1, respectively. The ground (X) state shows complex structure which may be interpreted as the result of a strong, but linear Jahn–Teller effect. Evidence is obtained for two pseudo-rotational progressions having states of vibronic angular momentum of j=±1/2,…,±7/2 based upon a1′ normal frequencies of 142.8 and 278.1 cm−1. This indicates a fluxional ground state with E symmetry in the D3h limit. No such effects are apparent in the low-lying excited states, although a1′ modes of 143–152 cm−1 are observed and in some cases geometrical information may be inferred. The ...

Spectroscopy of Mass-Selected Zirconium Dimers in Argon

We report absorption (“scattering depletion”) spectra and Raman measurements for Zr2 in an argon matrix prepared by the mass selected ion deposition technique. The principal dimer absorption bands occur at 388 nm and near 630 nm where we observe a vibrational progression with ω0′ = 225 (15) cm−1 for Tp = 15,230 (15) cm−1. Resonance Raman spectra, obtained by exciting into the 630 nm band, give ωe″ = 305.7 (35) cm−1 and ωexe″ = 0.5 (7) cm−1. The Raman data are consistent with either a 1Σg + or a 3Δg ground state.