Ulf Sassenberg

The 3Π0u ← X 3Δ1g band system of jet‐cooled Ti2

A band of jet‐cooled 48Ti2 has been located in the near infrared by resonant two‐photon ionization spectroscopy. Rotational analysis has shown the band to be an Ω’=0±←Ω‘=1 transition, which is consistent with the 3Δg ground state proposed by Bauschlicher et al. [J. Chem. Phys. 95, 1057 (1991)]. The band is assigned as a 3Π0u ← X 3Δ1g transition, and lower and upper state bond lengths have been determined as r0(X 3Δg)=1.9422±0.0008 A and r0(3Πu)=1.997±0.009 A (1σ error limits, corrected for spin–uncoupling effects). Comparisons are made to the TiV and V2 molecules, a rationale for the unusual filling order of the 3d‐based molecular orbitals is provided, and molecular orbital assignments are considered for the excited 3Πu state.

The 3Δu−X3Δg band system of jet-cooled Ti2

Abstract Jet-cooled Ti 2 has been observed around 9100 cm −1 using the resonant two-photon ionisation technique. A band at 9097 cm −1 has been analysed as a 3 Δ 1u ← X 3 Δ 1g transition while a weaker structure at 9093 cm −1 has tentatively been labelled 3 Δ 2u ←X 3 Δ 2g .

The Emission Spectrum of PtO Between 3800 Å and 8900 Å

The emission spectrum of PtO has been studied between 3800 A and 8900 A. In addition to the earlier reported A-X and D-X transitions several new transitions have been analysed. Most of them have either the X state or another state called the x state as their lower state. The X state has the character of a 0+ state, the x state has the character of a 1 state in Hunds coupling case c which together correspond to a 3Σ- state. The X state together with the x state seem to constitute the ground state of PtO. The following molecular constants in cm-1 were obtained:

The microwave spectrum of CuO, X 2Π, measured with optical detection

The microwave pure rotational transitions J=3/2←1/2 and 5/2←3/2 have been measured for gas phase CuO in its X 2Π state, using microwave‐optical double resonance. The copper hyperfine structure was observed, and has been analyzed for the first time for the ground state of an orbitally degenerate transition metal‐containing molecule in the gas phase. Rotational, lambda‐doubling, and magnetic and electric hyperfine parameters have been evaluated; the Fermi contact parameter bF has been found to be very large and negative. The problem of determining the signs of the ‘‘off‐diagonal’’ hyperfine parameters in 2Π electronic states is discussed.

On the Λ-type Doubling in the Ground State of SiH

The (0, 0) band of the 2?-2? transition of SiH has been remeasured from high-dispersion plates and more precise values of the ?-doubling parameters for the 2? state have been determined. From these optical measurements the transition between the two components of the lowest rotational level can be predicted to lie at 2968 ? 6 MHz.

R2PI detection of the quantum yields of I(2P1/2) and I(2P3/2) in the photodissociation of C2F5I, n-C3F7I, i-C3F7I and CH3I

Abstract Resonant two-photon ionization R2PI has been applied to the measurements of the quantum yields ϕ of iodine atoms in the fine structure states 2 P 1/2 and 2 P 3/2 arising in the UV-photodissociation process ( λ =266 and 355 nm) of the perfluoroalkyliodides C 2 F 5 I, n -C 3 F 7 I and i -C 3 F 7 I as well as of methyl iodide CH 3 I ( λ =266 nm). The measured values of the quantum yields of the excited state ( 2 P 1/2 ) of the I atoms are found to be ϕ 266 ∗ =0.921±0.010 and ϕ 355 ∗ =0.178±0.025 for C 2 F 5 I, ϕ 266 ∗ =0.919±0.011 and ϕ 355 ∗ =0.296±0.029 for n -C 3 F 7 I, ϕ 266 ∗ =0.900±0.015 and ϕ 355 ∗ =0.396±0.034 for i -C 3 F 7 I, and ϕ 266 ∗ =0.71±0.03 for CH 3 I. The results obtained show that the quantum yield ϕ 266 ∗ of the excited state atoms I( 2 P 1/2 ) in the photodissociation process of the perfluoroalkyliodides differs noticeably from unity which has previously been assumed or measured for these molecules.

Rotational and hyperfine analysis of the C4Σ−−X4Σ− (blue) system of niobium oxide, NbO

Abstract The C 4 Σ − - X 4 Σ − (0, 0) band of NbO, whose R heads lie near 4690 A, has been analyzed from high-resolution grating spectra. Both 4 Σ − states have second-order spin-orbit splittings, 4 λ = E( 4 Σ 3 2 )-E( 4 Σ 1 2 ) , of about 60 cm −1 , so that they are in good case (a) coupling at low J , although the appearance of the band had been interpreted by previous workers as 4 Σ( b )- 4 Σ( b ). the 93 Nb nuclear hyperfine structure ( I= 9 2 ) is very impressive in the R 1 , P 1 , R 4 , and P 4 branches, with the 10 hyperfine components of a rotational line spread over more than 0.9 cm −1 in the F 1 branches. The hyperfine linewidths vary considerably with J , in the manner expected for the rapid spin uncoupling from case (a β ) to (b β J ) which occurs in a high-multiplicity state. The very great hyperfine linewidths arise because the sign of the Fermi contact parameter b (the coefficient of I·S in the magnetic hyperfine Hamiltonian) is different in the two 4 Σ states, so that the observed patterns are the sums of the splittings in the two electronic states.

Resonant two-photon ionization spectroscopy studies of jet-cooled

Resonant two-photon ionization spectroscopy in a jet-cooled molecular beam has been employed for the study of the zirconium dimer produced by laser ablation. More than 110 resonances have been observed in the wavelength region 610-1070 nm. Most of these resonances are transitions from of the ground state, which is shown to be a state, to different vibrational levels of the excited states. Three bands have been rotationally analysed. The ground state B-value is found to be . Radiative lifetimes have been measured for two excited states, both of them between 1 and .

The Vacuum Ultraviolet Spectrum of Selenium Hydride I. Determination of the Ground State Spin-Orbit Coupling Constant

In the wavelength region 1700-1900 A an electronic transition in the SeH (SeD) molecule is observed. Even though the bands are so diffuse that the rotational structure is almost unresolved, the transition can be identified as the B2Σ-X2Πi system and a good determination of the spin-orbit coupling constant A = -1764.4 ± 0.2 cm-1 can be made.

Resonant tow-photon ionization detection of atomic iodine resulting from photodissociation of allyl iodide under vibrational (C-H overtone) excitation

Abstract The resonant two-photon ionization (R2PI or (1 + 1) REMPI) method was used to achieve highly sensitive detection of atomic iodine. The atoms were excited and ionized by tuned VUV and visible radiation, subsequently. The formation of iodine atoms in the fine structure states 2 P 3 3 2 and 2 P 1 2 was observed after the photolysis of allyl iodide (C 3 H 5 I) by UV radiation (355 nm). The atomic iodine absorption at 151.469 and 159.358 nm corresponding to the transitions 2 P 3 2 -( 3 P 2 ) 5d[3] 5 2 and 2 P 1 2 - 3 P 2 5d[2] 3 2 , respectively, were obtained under both collisional and collisionless conditions. It was shown, that the distribution of I atoms on hyperfine structure levels, produced from the photodissociation of C 3 H 5 I did not differ from the equilibrium one. The time-profile of atomic iodine appearance was measured when C 3 H 5 I was excited at the CH vibrational overtone frequency (υ=5, λ=703.5 nm).