O. Launila

Laser spectroscopy and density functional calculations on niobium monocarbide

A survey of the jet-cooled Nb12C and Nb13C radicals has been carried out between 13 500 and 18 000 cm−1 using laser-induced fluorescence and resonant two-photon ionization spectroscopy. Several vibronic bands belonging to at least six band systems have been identified. Three of these systems appear to belong to 2Π1/2–2Δ3/2 transitions in which the lower 2Δ3/2 state is the ground electronic state of the molecule. The other three systems also terminate to the same three 2Π1/2 upper states, but originate from a state lying 830 cm−1 above the X 2Δ3/2 state. This state is assigned as the A 2Σ+ state. The ionization potential has been determined to be 56 402±15 cm−1 or 6.9929±0.0018 eV using two-color photoionization efficiency spectroscopy. This value, combined with the ionization potential of Nb and the bond energy of NbC+, yields an improved bond energy of 5.39±0.15 eV for NbC. The (4,0) band of the B 2Π1/2–X 2Δ3/2 system has been studied at a resolution of approximately 0.005 cm−1 using laser-induced fluore...

The low-lying electronic states of CrF and CrCl: Analysis of the A 6Σ+→X 6Σ+ system of CrCl

A high-resolution near infrared spectrum of the CrCl radical has been recorded in thermal emission with Fourier transform techniques in the interval from 6 900 cm−1 to 11 500 cm−1. Two dominating band systems have been found in this region; (1) The A 6Σ+→X 6Σ+ system, analyzed in the present work, consisting of the (0,0), (0,1), (1,0), (2,0), and (3,0) bands, the (0,0) band being located at around 9450 cm−1; (2) the B 6Π→X 6Σ+ system, with a band interpreted as (0,0), located between 8700 cm−1 and 9000 cm−1, overlapping the (0,1) band of the A 6Σ→X 6Σ+ system. A rotational analysis of the A 6Σ+→X 6Σ+ system has been carried out, and the following principal parameters (cm−1) have been derived: X 6Σ+: ωe=396.6621, Be=0.167 587 3, De=1.1835⋅10−7; A 6Σ+: ωe=379.39, Be=0.156 51. Local perturbations in the A 6Σ+ (v=0,1) levels have been attributed to interactions with the B 6Π (v=1,2) levels. In the present work, we have constrained the investigations on the B 6Π→X 6Σ+ system to the verification that the lower ...

Spectroscopy of TiH: Rotational analysis of the 4Γ→X 4Φ (0,0) band at 530 nm

Emission bands of the TiH radical in the region 18 000–20 000 cm−1 have been recorded both with grating spectrograph and Fourier transform techniques. The rotational structure of the 530 nm band, which is the strongest one of the three observed bands, has been analyzed and molecular parameters have been derived for the electronic states involved. The electronic assignment of this band is confirmed as 4Γ→X 4Φ, with a heavily perturbed upper state. The principal parameters (cm−1) of the analyzed states are X 4Φ (v=0): A=33.083(29), B=5.362 06(19), and γ=0.1823(27). 4Γ (v=0): T=18 878.10(47), A=41.54(10), B=5.7408(22), γ=−4.33(12), and λ=0.77(14). The derived first order spin–orbit parameter values of X 4Φ and 4Γ are shown to be consistent with the electronic configurations δπσ and δππ′, respectively. The local perturbations in the 4Γ state are discussed and arguments are given to suggest that the dominating perturber is of 4Φ symmetry.

Spectroscopy of CrF: Rotational analysis of the B 6Π–X 6Σ+ band system in the 1.2 μm region

The B 6Π–X 6Σ+ band system of the CrF radical has been recorded in emission with FTS techniques in the region between 6965 and 9240 cm−1, using a resolution of 0.025 cm−1. A rotational analysis including the (0,0), (1,1), (1,0), (0,1) and (1,2) bands of this system has been carried out, and a set of molecular parameters has been derived for the B 6Π state. The present analysis has also resulted in substantially better determined values for the λ and γ parameters of the X 6Σ+ ground state. An improved set of molecular parameters has been derived for the previously analyzed, heavily perturbed A 6Σ+ state. The present analysis gives strong support for the interpretation that the local perturbations in the v=0–3 levels of A 6Σ+ are due to interactions with the vibrational levels v=3–6 of the B 6Π state. Earlier suggestions involving a low‐lying 4Π state as the dominating perturber of the A 6Σ+ state must now be considered as erroneous. A previously suggested interpretation of the 7400 cm−1 band as being possi...

The C3Δ-X3Δ, A3Φ-X3Δ and E3Π-X3Δ systems of TiS

The thermal emission spectrum of TiS has been recorded with Fourier transform spectroscopy in two different regions, 10 000–12 600 cm-1 and 6 000–8 600 cm-1, with a resolution of 0·05 cm-1. The first region covers the C3Δ-X3Δ system while the second region covers the previously unobserved A3Φ-X3Δ and E3Π-X3Δ systems. Lines from 18 different vibrational bands were included in the analysis. Of these, 9 belong to the C3Δ-X3Δ system, 8 to the A3Φ-X3Δ system, while only the (0, 0) band was observed in the E3Π-X3Δ system. No satellite transitions were observed. Molecular constants have been determined for the four states. A perturbing state causing the observed local perturbations in the C3Δ1 substate is suggested. The electron configurations of the four states have been discussed in terms of observed bond lengths.

Spectroscopy of MnF: Rotational and hyperfine analysis of the c5Σ+-a5Σ+ transition near 690 nm

Abstract A band system near 690 nm in MnF has been studied at low temperature by laser-induced fluorescence in a supersonic jet, and at high temperature by conventional hollow cathode techniques. The electronic transition lies within the quintet manifold and is here designated c 5 Σ + - a 5 Σ + . All the 10 main branches and 11 satellite branches have been identified in the (0, 0) band with the help of the resolved hyperfine structure. Three of the satellite branches are induced by an avoided crossing of the F 3 and F 4 components of the upper state near N ′ = 8. One further satellite branch is induced by another avoided crossing of F 2 and F 3 near N ′ = 4. Rotational, fine, and hyperfine constants have been determined for both states through combined use of high- and low-temperature data. Fragments of the (1, 1) band have also been included in the analysis.

Spectroscopy and MRCI calculations on CrF and CrCl

The B 6Π–X 6Σ+ band system of the CrCl radical has been recorded in thermal emission with FTS techniques in the region 6900–11 700 cm−1, using a resolution of 0.025 cm−1. An analysis of the (0,0) band of this system has been carried out. A rotational constant of B0=0.1615 cm−1 and a spin–orbit parameter of A0=51 cm−1 have been estimated for the B 6Π state. Improved values for the γ and λ parameters of the X 6Σ+ ground state have been obtained. MRCI calculations have been performed on CrF and CrCl and comparisons have been made with both experiments and DFT calculations [Bencheikh et al., J. Chem. Phys. 106, 6231 (1997)]. The calculations on CrF have provided valuable aids in the interpretations of the fluorescence excitation and dispersed fluorescence spectra of a state observed at 31 700 cm−1. This state has now been assigned as D 6Π. A number of transitions in the dispersed fluorescence spectra are believed to involve the hitherto unknown C 6Δ state. Spin–orbit-configuration-interaction (SO-CI) calculat...

Fourier transform spectroscopy of MnH and MnD: Rotational analyses of the 846 nm and 1060 nm systems

Two infrared band systems, centred near 846 nm and 1060 nm in both MnH and MnD have been rotationally analysed and shown to have a common lower state. The electronic transitions lie within the quintet manifold and are here designated c 5Σ-a 5Σ and b 5Π i -a 5Σ for the 846 and 1060 nm systems, respectively. In the 846 nm system in MnH all 10 main branches have been found in the 0-0 and 1-1 bands, while in MnD the data are complete only for 0-0. Satellite branches have been identified in the 1060 nm system and all spin and Λ-type doublings have been established. The number of assigned 0-0 branches in the 1060 nm system is 35 for MnH and 37 for MnD. Molecular constants have been determined for all three states involved. Λ-doubling diagrams are presented for b 5Π i state with v = 1, 2 levels in MnH and with the v = 2 level in MnD. Local perturbations in c 5Σ (v = 1) in MnH are suspected to originate from the v = 3 level of b 5Π i .

Raman spectra of P4 at low temperatures

Raman spectra of solid P4 have been recorded from 12 K up to room temperature using Fourier transform-Raman spectroscopy. The three Raman-active modes corresponding to Td symmetry have been resolved, and line shifts depending on temperature and matrix environment have been measured. Two phase transitions have been observed at T≈80 K (irreversible) and T≈195 K (reversible) corresponding to the γ→β and β↔α transitions, respectively. In the β phase, the ν2 mode is split into two lines, νsplit≈7.7 cm−1. The splitting of the ν2 mode is an indication of a breaking of Td symmetry for the β phase. A matrix shift of ≈3 cm−1 for P4 in a N2 matrix (1:5) was measured. Comparing experimental transitions of pure P4 with literature values on matrix isolated P4 in N2 (1:1000) we can conclude that there is a matrix shift in nitrogen of between 6 and 9 cm−1 depending on vibrational mode. The line positions found for pure P4 in the γ phase at 12 K are ν1=599.8 cm−1, ν2=361.6 cm−1, and ν3=459.0 cm−1. The corresponding values...

Spectroscopy of MnCl: vibrational analysis of a band system near 877 nm and observation of a new band system near 1001 nm

A band system in MnCl near 877 nm has been vibrationally analysed, and the analysis is not in accord with literature results. The present analysis indicates that the transition involved is a c5Σ+ - a5Σ+, as already analysed in MnH/D and in MnF. A new band system centred at 1001 nm has been recorded.