Fourier transform emission spectroscopy and ab initio calculations on NbCl

The emission spectrum of NbCl has been recorded in the 3000-20 000 cm⁻¹ region using a Fourier transform spectrometer. The bands were observed by microwave excitation of a mixture of NbCl₅ vapor and He. Two groups of bands observed in the 6500-7000 cm⁻¹ and 9800-11 000 cm⁻¹ regions have been assigned to two electronic transitions. Five bands observed in the 6500-7000 cm⁻¹ region consist of R, P, and Q branches with no combination defect or Λ-doubling. They have been assigned as five sub-bands of a ΔΛ=±1 transition with Λ>1. Nine bands observed in the 9800-11 000 cm⁻¹ regions consist of R and P branches, and they are also free from Λ-doubling. These bands have been classified into four sub-bands of a ΔΛ=0 transition (with Λ>1), which has tentatively been assigned as . The two transitions have no electronic states in common. Ab initio calculations have been performed on NbCl and the spectroscopic properties of the low-lying electronic states have been calculated. The ground state of NbCl has been predicted to be a state arising from the 3σ¹ 1δ² 2π¹ configuration, with a low-lying state at 1300 cm⁻¹ from the 3σ¹ 1δ¹ 2π² configuration. The results of our experimental and theoretical studies will be presented. This work represents the first experimental investigation of the spectra of NbCl and the first ab initio prediction of the spectroscopic properties of the low-lying electronic states.     

Laser spectroscopy of the A[16.4]8.5-X7.5, A[16.4]8.5-Y[0.15]8.5, and A[16.4]8.5-Z[0.85]7.5 transitions of dysprosium monochloride

Laser-induced fluorescence spectra have been obtained at low resolution using a laser ablation source and pulsed dye laser, and at high resolution using a Broida oven and cw ring dye laser. Dispersed fluorescence spectra from two different excited states, A[16.4]8.5 and B[15.4]Ω (unknown Ω) (the states are labelled [10⁻³T₀]Ω according to their energy and Ω assignment) showed transitions to the same four low lying electronic states, X7.5, Y[0.15]8.5, Z[0.85]7.5, and an unassigned state at 970 cm⁻¹. High resolution excitation spectra of the A-X 0-0, A-Y 0-0 and 0-1, and A-Z 0-0 and 0-1 transitions were obtained and a global fit to all the data yielded rotational constants for both ¹⁶²Dy³⁵Cl and ¹⁶⁴Dy³⁵Cl. From the band origins, vibrational frequencies of 291 and 284 cm⁻¹ were obtained for the Y[0.15]8.5 and Z[0.85]7.5 states, respectively, suggesting that these two states originate from the Dy⁺(4f¹⁰6s)Cl⁻ configuration. The ¹⁶²Dy-¹⁶⁴Dy and ³⁵Cl-³⁷Cl isotope effects were studied and both indicated a ground state, X7.5, vibrational frequency of ∼230 cm⁻¹ which was reinforced by the observation, in dispersed fluorescence from the B[15.4] state, of a weak transition to a state 233 cm⁻¹ above the ground state. The observed electronic states and their configurational origin are discussed in terms of ligand field theory predictions.     

Fourier transform emission spectroscopy and ab initio calculations on WO

Emission spectra of WO have been observed in the 4000-35 000 cm⁻¹ region using a Fourier transform spectrometer. Molecules were produced by exciting a mixture of WCl₆ vapor and He in a microwave discharge lamp. A ³Σ⁻ state has been assigned as the ground state of WO based on a rotational analysis of the observed bands and ab initio calculations. After rotational analysis, a majority of strong bands have been classified into three groups. Most of the transitions belonging to the first group have an Ω = 0⁺ state as the lower state while the bands in the second group have an Ω′′ = 1 state as the lower state. These two lower states have been assigned as X0⁺ and X1 spin components of the X³Σ⁻ ground state of WO. The third group consists of additional bands interconnected by common vibrational levels involving some very low-lying states. The spectroscopic properties of the low-lying electronic states have been predicted from ab initio calculations. The details of the rotational analysis are presented and an attempt has been made to explain the experimental observations in the light of the ab initio results.     

Laser spectroscopy of holmium monosulphide: Electronic, vibrational and rotational structure of the A[14.79]8.5-X8.5, A[14.79]8.5-W[0.25]7.5 and A[14.79]8.5-V[0.98]7.5 transitions

Laser induced fluorescence spectra of HoS have been obtained using a Broida oven and a ring dye laser. Dispersed fluorescence spectra showed transitions from a common upper state, A[14.79]8.5 to the v = 0 and 1 vibrational levels of three low lying states, labelled X8.5, W[0.25]7.5 and V[0.98]7.5 (the states are labelled [10⁻³T₀]Ω according to their energy and Ω assignment). High resolution excitation spectra were obtained for all six transitions and a rotational analysis yielded the following principal constants, in cm⁻¹, for the X, W and V states, respectively: T₀ = 0, 251.8713(31), 980.6969(37); B_e = 0.121903(42), 0.121729(37), 0.122561(34); ΔG_1/2 = 463.8811(46), 462.9411(45), 461.2084(127). For the A state, T₀ = 14794.6987(28) cm⁻¹ and B₀ = 0.112596(29) cm⁻¹. The three low lying states are shown to arise from the Ho²⁺[4f¹⁰(⁵I₈)6s]S²⁻ configuration in accord with Ligand Field Theory predictions. The atomic origin of each of the three low lying electronic states was determined from the observed resolved hyperfine structure.     

Laser and Fourier transform emission spectroscopy of TaCl

The emission spectrum of TaCl has been recorded at high resolution in the 3000-35 000 cm⁻¹ region using a Fourier transform spectrometer. The bands were observed by microwave excitation of a mixture of TaCl₅ vapor and 3.0 Torr of He. Several TaCl bands have also been recorded using the laser ablation/molecular beam source at the University of New Brunswick. A rotational analysis of a number of bands has been obtained and the majority of the stronger bands have been classified into three groups with different lower state spectroscopic constants. The three lower states have been identified as having Ω″ = 0⁺, Ω″ = 2, and (tentatively) Ω″ = 3. The Ω″ = 0⁺ and Ω″ = 2 states are very close in energy and one of these two states is the ground state of TaCl.     

The laser-induced fluorescence spectroscopy of CoF in the ultra violet region

The laser-induced fluorescence (LIF) spectrum of jet-cooled CoF has been obtained in the wavelength region of 260-290 nm for the first time. Seventeen vibronic bands were observed and assigned to three types of transition from the ground state to upper states Ω′ = 3, 4, 5 by rotational analysis. A new vibrational transition with the 0-0 band at 34697.22 cm⁻¹ has been assigned as the [34.7]³Γ₅-X³Φ₄ transition and effective equilibrium molecular constants for the upper state have been determined. In addition, lifetime measurements have been carried out for most of the bands under collision-free conditions. On the basis of the spectroscopic data and lifetime measurements, the electronic structures of these possible high-lying electronic states are discussed.     

Spectroscopy of NdO: New results

¹⁴²NdO molecules have been produced by heating ¹⁴²Nd₂O₃ to about 2100 K in a vacuum furnace in the presence of argon gas. A ring dye laser operating with DCM dye has been used to excite ¹⁴²NdO transitions in the 636-666 nm spectral region, and induced fluorescence has been spectroscopically analysed at high resolution with a Fourier transform spectrometer. Contributions from thermal emission have been simultaneously observed. Two new low-lying electronic states have been detected, at energies of about 2708 and 4139 cm⁻¹, designated as [2.7], most probably observed at ν = 1, and [4.1], likely to be (2)6 (observed at ν = 0). The ν = 1 level of the (1)6 state, already known at ν = 0, has been observed for the first time. Most levels pumped by the laser, between 14 000 and 17 400 cm⁻¹, could be identified from earlier work. In addition, by studying in more detail recently obtained fluorescence spectra [J. Mol. Spectrosc. 225 (2004) 132] spectroscopic constants have been improved for a number of states. Finally, from thermal emission spectra, rotational analyses of the 0-0 bands of two new systems, [16.4] − (2)5 and [14.1] − X4, and reanalyses at higher resolution of the 0-0 bands of the systems V, VII, VIII, and X have been carried out. A consistent set of spectroscopic constants of the levels of ¹⁴²NdO characterized as yet is presented.     

High-resolution visible laser spectroscopy of HfF

The electronic spectrum of hafnium monofluoride has been investigated from 415 to 725 nm using a laser-ablation/molecular beam laser-induced fluorescence spectrometer. Several electronic systems were observed and data have been recorded at both low and high resolution. High resolution rotational analyses of the [17.4]1.5-X1.5 (0-0), [17.9]2.5-X1.5 (0-0), [19.7]0.5-X1.5 (0-0), [20.0]0.5-X1.5 (0-0), [21.1]2.5-X1.5 (0-0), [22.3]1.5-X1.5 (0-0), and [23.3]0.5-X1.5 (0-0) subbands have been carried out, resulting in accurate values for the ground and excited state effective rotational constants. Furthermore, the rotational analysis of the subbands assigned as [17.4]1.5-X1.5 (1-0) and [17.9]2.5-X1.5 (1-0) allows us to determine values of 589.7569(6) and 588.9076(6) cm⁻¹ for ΔG^′_1/2 [17.4] and ΔG^′_1/2 [17.9], respectively. From dispersed fluorescence data we find that ΔG^′′_1/2=670(13) cm⁻¹ for the ground state and that another low-lying electronic state lies at ∼2850 cm⁻¹. The data also suggests that a second low-lying electronic state lies at ∼5200 cm⁻¹ above the ground state.     

Laser spectroscopy of the B[17.7]8-X8 and C[19.3]9-X8 transitions of holmium monochloride

Several new transitions of holmium monochloride (HoCl) have been studied at high resolution using laser excitation spectroscopy. Two main transitions, B[17.7]8-X8 and C[19.3]9-X8 have been observed and five bands, 0-0, 0-1, 1-0, 1-1, and 2-1 of the B-X transition and three bands, 0-0, 0-1, and 0-3 of the C-X transition have been obtained at high resolution and rotationally analyzed. Among several low lying states observed in dispersed fluorescence was a strong transition from the C state to a state ∼2140 cm⁻¹ above the ground state. Excitation spectra of this transition have shown that there are apparently two states, ∼6 cm⁻¹ apart. Comparison with ligand field theory calculations are consistent with assigning these states to the excited low lying Ho⁺(4f¹¹6s)Cl⁻ configuration. Several other low lying electronic states have been observed in dispersed fluorescence spectra. Although their assignments could not be established, their energies suggest that they are from the Ho⁺(4f¹⁰6s²)Cl⁻ or Ho⁺(4f¹¹6s)Cl⁻ configurations. Rotational constants have been obtained for the B[17.7]8 and C[19.3]9 states and have been used to speculate on the possible electron configurations for these states.     

Intracavity laser absorption spectroscopy of platinum fluoride, PtF

Two vibrational bands of an electronic transition of PtF occurring at 11 940 cm⁻¹ and 12 496 cm⁻¹ were recorded and analyzed. These transitions are identified as the (0,0) and (1,0) bands of an [11.9] Ω = 3/2 − XΩ = 3/2 electronic transition. Gas phase PtF was produced in a copper hollow cathode lined with platinum foil using a trace amount of SF₆, and the spectrum was recorded at Doppler resolution by intracavity laser absorption spectroscopy. This work represents the first published spectroscopic data on PtF. Molecular constants for the ground and excited electronic states are presented.     

Growth and spectroscopic characterization of Er: Sr3Y(BO3)3 crystal

This paper reports the growth and spectroscopic characterization of Er³⁺:Sr₃Y(BO₃)₃ crystal. Er³⁺:Sr₃Y(BO₃)₃ crystal with dimensions up to ∅20×35 mm³ has been grown by Czochralski method. The polarized spectroscopic properties of Er³⁺:Sr₃Y(BO₃)₃ crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ω_t were obtained: Ω₂=1.71×10⁻²⁰ cm², Ω₄=1.39×10⁻²⁰ cm², Ω₆=0.74×10⁻²⁰ cm² for π-polarization, and Ω₂=1.77×10⁻²⁰ cm², Ω₄=1.44×10⁻²⁰ cm², Ω₆=0.65×10⁻²⁰ cm² for σ-polarization. The emission cross-section σ_em was calculated to be 4.75×10⁻²¹ cm² for π-polarization at 1536 nm and 6.30×10⁻²¹ cm² for σ-polarization at 1537 nm. The investigated results showed that Er³⁺:Sr₃Y(BO₃)₃ crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers.     

A visible spectrum of jet-cooled rhodium monosulfide

The diatomic molecule RhS has been observed for the first time. It has been studied by high resolution laser-induced fluorescence spectroscopy in a supersonic molecular beam following reaction by laser-vaporized rhodium atoms with CS₂ doped in He. Electronic, vibrational, and rotational data have been collected. The RhS ground state has ⁴Σ⁻ symmetry with a second-order spin-orbit splitting of 47.43 cm⁻¹, indicating case (a) coupling at low J. Three bands in the 535-555 nm region have been rotationally analyzed and give a bond length in the ground state of 0.2059 nm. A vibrational frequency ω_e ≈ 485 cm⁻¹ is estimated from dispersed fluorescence measurements.     

Spectra and intensity parameters of Tm ion in YAlO3 crystal

High quality Tm-doped YAlO₃ (Tm:YAlO₃) single crystals were obtained along crystallographic b-axis by the Czochralski technique. Optical absorption and fluorescence spectra for Tm³⁺ in YAlO₃ crystals were investigated at room temperature. Based on Judd-Ofelt approach, the intensity parameters Ω_t (t = 2, 4, 6) of Tm:YAlO₃ were calculated to be Ω₂ = 0.93 × 10⁻²⁰  cm², Ω₄ = 2.23 × 10⁻²⁰ cm², and Ω₆ = 1.12 × 10⁻²⁰ cm². The spectral parameters such as experimental and theoretical oscillator strengths, radiative transition probabilities, radiative lifetime and the fluorescence branching ratio were also obtained. All results indicate that Tm:YAlO₃ is a potential candidate for compact, efficient mid-infrared lasers with laser diode pumping.     

Laser-Induced Fluorescence Molecular Beam Investigation of New Singlet and Triplet Electronic States of Yttrium Monohydride

The yttrium monohydride spectrum in the range 12 500-25 000 cm⁻¹ has been studied by various laser-induced fluorescence (LIF) techniques. YH (YD) molecules have been produced in a free jet molecular beam apparatus by a laser vaporizing yttrium metal in the presence of He doped with H₂ (D₂) or NH₃ (ND₃). Low-resolution (∼0.04 cm⁻¹) excitation spectra have been recorded in the entire studied range. Four green bands (19 300-19 900 cm⁻¹) of the YH isotopomer have been studied in more detail: (1) high-resolution (∼120 MHz, ∼0.004 cm⁻¹) excitation spectra have been recorded, (2) dispersed fluorescence spectra have been obtained, and (3) lifetimes of the selected rotational levels of the upper states have been measured. Our observations have confirmed that the ground state of yttrium monohydride has ¹Σ⁺ symmetry and have provided a link between the singlet and triplet manifolds. The upper states of the observed transitions have been tentatively assigned to five electronic states, d0⁺, f³Π, f′1, D¹Π, E0⁺, and Fl. The low-energy excited electronic state observed in the dispersed fluorescence experiment has been assigned as the a³Δ state.     

Laser excitation spectrum of C3 in the region 26 000-30 700 cm

The vibrational structure of the electronic state of C₃ in the region 26 000-30 775 cm⁻¹ has been re-examined, using laser excitation spectra of jet-cooled molecules. Rotational constants and vibrational energies have been determined for over 60 previously-unreported vibronic levels; a number of other levels have been re-assigned. The vibrational structure is complicated by interactions between levels of the upper and lower Born-Oppenheimer components of the state, and by the effects of the double minimum potential in the Q₃ coordinate, recognized by Izuha and Yamanouchi [16]. The present work shows that there is also strong anharmonic resonance between the overtones of the ν₁ and ν₃ vibrations. For instance, the levels 2 1⁺ 1 and 0 1 ⁺ 3 are nearly degenerate in zero order, but as a result of the resonance they give rise to two levels 139 cm⁻¹ apart, centered about the expected position of the 2 1⁺ 1 level. With these irregularities recognized, every observed vibrational level up to 30 000 cm⁻¹ (a vibrational energy of over 5000 cm⁻¹) can now be assigned. A vibronic level at 30181.4 cm⁻¹, which has a much lower B′ rotational constant than nearby levels of the state, possibly represents the onset of vibronic perturbations by the electronic state; this state is so far unknown, but is predicted by the ab initio calculations of Ahmed et al. [36].     

Influence of B2O3 to the inhomogeneous broadening and spectroscopic properties of Er/Yb codoped fluorophosphate glasses

In a three-components fluorophosphate glass system, the introduction of H₃BO₃ brings some valuable influence to the spectroscopic and thermal properties of the glasses. With H₃BO₃ increases from 2 to 20 mol%, Ω₆, S_ed4I13/2, FWHM, T_g and fluorescence lifetime change from 3.21×10⁻²⁰ cm², 1.77×10⁻²⁰ cm², 45 nm, 480 °C and 8.8 ms to 4.66×10⁻²⁰ cm², 2.11×10⁻²⁰ cm², 50 nm, 541 °C and 7.4 ms, respectively. σ_abs, σ_emi, FWHM×τ_f×σ_emi has a maximum when H₃BO₃ is 11 mol%. T_g and T_x−T_g increases with H₃BO₃ introduction. Results showed that in fluorophosphate glasses, proper amount of B₂O₃ can be used as a modifier to suppress upconversion and improve spectroscopic properties, broadband property and crystallization stability of the glasses while keeps the fluorescence lifetime relatively high.     

Laser spectroscopy of the B[21.68]8-X8, B′[21.65]8-X8 and C[22.3]7-X27 transitions of holmium monofluoride

The spectrum of holmium monofluoride (HoF) in the blue (420-480 nm) region has been studied using laser-induced fluorescence. Previous work [J. Phys. B 7 (1974) L234] had assigned several bands in this region to the B8-X8 transition. By obtaining wavelength selected laser excitation spectra at high resolution and rotationally analyzing seven bands in this region, we have shown that not all the bands previously assigned to the B8-X8 system belong to the same electronic transition and have identified three separate transitions which we have labelled B8-X8, B′8-X8, and C7-X₂7. Preliminary low resolution dispersed fluorescence spectra have shown several excited states at energies greater than 4000 cm⁻¹ above the ground state and, though not all could be assigned, ligand field theory calculations are consistent with assigning them to the first excited spin-orbit component of the Ho⁺(4f¹⁰6s²)F⁻ ground state configuration or to the first excited configuration, Ho⁺(4f¹¹6s)F⁻. The results of the dispersed fluorescence experiments also tentatively place the X₂7 state at ∼70 cm⁻¹ above the ground X7 state.     

High-Resolution Visible Laser Spectroscopy of Cobalt Monochloride

The electronic spectrum of cobalt monochloride has been investigated from 415 to 725 nm using a laser-ablation/molecular-beam laser-induced fluorescence spectrometer. Two separate electronic systems with origins near 483.3 and 470.3 nm were observed. Data have been recorded for these two transitions at both low and high resolution. These transitions are now characterized as the [20.7]³Φ₄−X³Φ₄ and [21.3]³Φ₄−X³Φ₄ transitions. A low-resolution vibrational analysis and a high-resolution rotational analysis have been carried out for each system, resulting in accurate values for the ground and excited state vibrational spacings and effective rotational constants. In addition, the magnetic hyperfine structure resulting from the spin of the Co nucleus was resolved and the hyperfine constants were determined. Comparison of the CoCl spectrum with that of CoH and CoF has allowed the ground state electron configuration of (core)(10σ)²(4π)⁴(1δ)³(5π)³(11σ)² to be determined. The hyperfine constants support the electron promotion 11σ→12σ for the observed transitions.     

Spectral properties of Nd:Ca2Nb2O7 crystal

This paper reports the spectral properties of Nd³⁺:Ca₂Nb₂O₇. The spectral parameters of Nd³⁺ in Nd³⁺:Ca₂Nb₂O₇ crystal have been investigated based on Judd-Ofelt theory. The spectral parameters were obtained. The parameters of line strengths Ω_λ are Ω₂=4.967×10⁻²⁰ cm², Ω₄=5.431×10⁻²⁰ cm², Ω₆=5.693×10⁻²⁰ cm². The radiative lifetime, the fluorescence lifetime and the quantum efficiency are 122 μs, 103 μs and 84.4%, respectively. The fluorescence branch ratios calculated: β₁=0.425, β₂=0.479, β₃=0.091, β₄=0.004. The emission cross section at 1068 nm is 6.204×10⁻²⁰ cm².