Dale J. Brugh

Optical spectroscopy of jet-cooled FeC between 12 000 and 18 100 cm−1

Iron monocarbide has been investigated between 12 000 and 18 100 cm−1 in a supersonic expansion by resonant two-photon ionization spectroscopy. Six new electronic states have been identified for which origins relative to the ground state have been determined. Three of these possess Ω′=3, one possesses Ω′=4, and two possess Ω′=2. The Ω′=3 state with an origin near 13 168 cm−1 is likely a 3Δ3 state and has been assigned as the analog of the [14.0]2Σ+←X2Σ+ charge transfer transition in CoC. The Ω′=4 state is most likely a 3Φ4 state. Additionally, seven bands with Ω′=2 have been observed that have proven impossible to systematically group by electronic state. Because every transition rotationally resolved in this study possesses a lower state with Ω=3, the ground state has been confirmed as arising from an Ω=3 state that is most likely the Ω=3 spin orbit component of a 3Δi term derived from a 1δ39σ1 configuration. The ionization energy (IE) of FeC has been determined as 7.74±0.09 eV by varying the wavelength ...

First spectroscopic investigation of the 4d transition metal monocarbide MoC

The first optical spectroscopic investigation of MoC has revealed a complicated vibronic spectrum consisting of about 35 bands between 17 700 and 24 000 cm−1. Analysis has shown the ground state to be the Ω=0+ spinorbit component of a 3Σ− state that derives from a 10σ211σ25π42δ2 configuration. The X 3Σ0+− rotational constant for 98Mo12C was determined to be B0=0.553 640±0.000 055 cm−1, giving r0=1.687 719±0.000 084 A. Consideration of spin-uncoupling effects in the X 3Σ− state requires that this value be revised to r0=1.6760 A, which represents our best estimate of the true Mo–C bond length. Spectroscopic constants were also extracted for six other major isotopic modifications of MoC in this mass resolved experiment. All rotationally resolved transitions were found to originate from the ground state and terminate in electronic states with Ω=1. An attempt is made to classify the observed transitions into band systems, to rationalize the complexity of the spectrum, and to understand the bonding from a molec...

Resonant two-photon ionization spectroscopy of NiC

A spectroscopic investigation of jet-cooled diatomic NiC has revealed a complex pattern of vibronic levels in the wave number range from 21 700 to 27 000 cm−1. Of the more than 50 vibronic bands observed, 31 have been rotationally resolved and analyzed. All are Ω′=0+←Ω″=0+ transitions, consistent with the calculated 1Σ+ ground state of this molecule. Through the observation of vibrational hot bands in the spectra, these measurements have established that ωe″=875.155 cm−1, ωexe=5.38 cm−1, Be=0.640 38(14) cm−1, αe=0.004 44(36) cm−1, and re=1.6273(2) A for 58Ni12C. Several possible electronic band systems are observed, but the identification of these is hampered by extensive perturbations among the excited states. The observation of long-lived vibronic states as far to the blue as 26 951 cm−1 indicates that D0(NiC)⩾3.34 eV, and the ionization energy of NiC has been determined to fall in the range IE(NiC)=8.73±0.39 eV. A discussion of these results, in the context of work on other 3d transition metal carbides...

Spectroscopic analysis of the open 3d subshell transition metal aluminides: AlV, AlCr, and AlCo

Three open 3d subshell transition metal aluminides, AlV, AlCr, and AlCo, have been investigated by resonant two‐photon ionization spectroscopy to elucidate the chemical bonding in these diatomic molecules. The open nature of the 3d subshell results in a vast number of excited electronic states in these species, allowing bond strengths to be measured by the observation of abrupt predissociation thresholds in a congested optical spectrum, giving D00(AlV)=1.489±0.010 eV, D00(AlCr)=2.272±0.009 eV, and D00(AlCo)=1.844±0.002 eV. At lower excitation energies the presence of discrete transitions has permitted determinations of the ground state symmetries and bond lengths of AlV and AlCo through rotationally resolved studies, giving r0‘ (AlV, Ω‘=0)=2.620±0.004 A and r0‘ (AlCo, Ω‘=3)=2.3833±0.0005 A. Ionization energies were also measured for all three species, yielding IE(AlV)=6.01±0.10 eV, IE(AlCr)=5.96±0.04 eV, and IE(AlCo)=6.99±0.17 eV. A discussion of these results is presented in the context of previous work ...

Resonant two-photon ionization spectroscopy of jet-cooled PtSi

Jet-cooled diatomic PtSi, produced in a laser ablation supersonic expansion source, has been spectroscopically investigated between 17 400 and 24 000 cm−1 by resonant two-photon ionization spectroscopy. Two vibrational progressions are observed and identified as the [15.7]Ω′=1←X 1Σ+ and [18.5]Ω′=1←X 1Σ+ band systems. Three bands in the former system and six bands in the latter system were rotationally resolved and analyzed, leading to bond lengths of re′=2.1905(13) A and re′=2.2354(3) A for the [15.7]Ω′=1 and [18.5]Ω′=1 states, respectively. The Ω″=0 ground state of PtSi is assigned as a 1Σ+ state, in agreement with previous work and with the assigned ground states of the isovalent NiC, PdC, PtC, and NiSi molecules. The ground state bond length of PtSi is given by r0″=2.0629(2) A. A Rydberg–Klein–Rees analysis of the ground and excited state potential energy curves is presented, along with a discussion of the chemical bonding and a comparison to the isoelectronic molecule, AlAu. Evidence is presented for ...

Optical spectroscopy of jet-cooled NiSi

The electronic states of gaseous diatomic NiSi have been investigated using the combined techniques of resonant two-photon ionization spectroscopy, dispersed fluorescence spectroscopy, and density functional computations. A single electronic band system, designated as the [18.0]1←X 1Σ+ system, has been found in the 17 500–19 500 cm−1 range, and three bands of this system have been rotationally resolved and analyzed. To shorter wavelengths, the spectrum becomes much more congested and intense, and four bands in this region have been rotationally resolved and analyzed as well. A dispersed fluorescence investigation has allowed the measurement of 17 vibrational levels of the ground state. Through this work, the ground state of 58Ni28Si is demonstrated to have 1Σ+ symmetry, with r0=2.0316(4) A, ωe=467.43(30) cm−1, and ωexe=2.046(21) cm−1. These results are in good agreement with the results of density functional computations performed on the ground state. Comparisons to AlCu and CuSi demonstrate that NiSi has...

Resonant two-photon ionization spectroscopy of the 13-electron triatomic Si2N

Abstract Resonant two-photon ionization spectra of 28Si2N, 28,29Si2N, and 28,30Si2N have been collected between 32000 cm−1 and 36000 cm−1. A fit of the rotationally resolved spectrum of the most intense band of 28Si2N at 34314 cm− reveals the transition to be 2 Σ u + a X 2 ∏ g , 1 2 . A molecular orbital analysis is made to justify the assignment. The geometric structure is determined to be linear and centrosymmetric in both the ground and excited state with r 0 ″ ( SiN ) = 1.6395 ± 0.0014 A and r′( SiN ) = 1.6343 ± 0.0014 A . The ionization energy energy is determined to be less than 8.51 eV.

Spectroscopy of jet-cooled YCu

Optical spectra of jet‐cooled diatomic YCu have been recorded using resonant two‐photon ionization spectroscopy in a supersonic expansion of helium. The ground state is shown experimentally to be of 1Σ+ symmetry, with a measured bond length of re‘=2.6197(6) A and a vibrational frequency of 193.21(24) cm−1 for 89Y63Cu. Five excited electronic states are identified as the [10.2]1Σ+ state, the [11.8]3Π0+ state, the [12.0]3Π1 state, the [14.0]1Π state, and, with the help of ab initio theory, the [12.2]1Π state. No evidence whatever for participation of the 3d orbitals of copper in the chemical bonding is found, and the electronic structure of YCu is found to exhibit a striking similarity to that of YH.

Radiative Lifetime of the v = 0, 1 Levels of the A 6Σ+ State of CrH

The time-delayed resonant two-photon ionization method has been used to measure the radiative lifetimes of the v = 0 and 1 levels of the A 6Σ+ state of CrH, yielding values of 0.939 ± 0.019 and 1.027 ± 0.066 μs, respectively (1 σ error limits). These measured lifetimes are about 16%-45% longer than those obtained in recent ab initio calculations, a result that is important for modeling of the atmospheric concentration of CrH in the class of substellar objects known as brown dwarfs. Based on these results, it is suggested that the line strengths used to calculate the opacity function used by astronomers should be reduced by a factor of 0.799. In addition, line positions are reported for the 0-0 band of the A 6Σ+-X 6Σ+ system of the minor isotope 50CrH, along with a least-squares fit of the lines to the standard matrix Hamiltonian.

Structure and dynamics of N2–IH

The ground state rotational spectra and internal dynamics in five isotopomers 14N2–IH, 14N2–ID, 15N2–IH, 14N15N–IH, and 15N14N–IH of the nitrogen–hydrogen iodine dimer have been investigated by pulsed-nozzle, Fourier-transform microwave spectroscopy. Analysis of the recorded spectra yields rotational, centrifugal distortion, nuclear quadrupole and spin-rotation coupling constants for the five isotopomers. The spectroscopic constants are interpreted in terms of a ground-state NN–IH structure using the parameters rcm, kσ, and the oscillation angles θN2 and θHI of the N2 and IH moieties. For 14N2–IH, the values rcm=4.197 872(67) A, kσ=1.461 52(32) N/m, θN2=25.61(22)°, and θHI=23.454 6(91)° are obtained. The rotational transitions of 14N2–IH, 14N2–ID, and 15N2–IH show a doubling, which is a consequence of tunneling associated with the interchange of the two nitrogen nuclei. The experimental findings are compared with results from ab initio calculations.