Fourier transform emission spectroscopy of CoCl in the 500 nm region

Fourier transform emission spectra of CoCl were obtained with a tube furnace-DC discharge source in the 450-500 nm spectral region. In addition to observing two different band systems, which were assigned as [20.7] and [21.3] by Adam et al. [J. Mol. Spectrosc. 212 (2002) 111], we obtained data for additional sub-bands and vibrational levels. In contrast to the previous work, intense Q branches are seen in the [21.3]- bands which indicate that these bands are likely ΔΛ≠0 transitions. The equilibrium rotational constant B_e for the ground state is 0.1801104(28) cm⁻¹, the equilibrium bond length is 2.065122(16) Å and ΔG_1/2 is 430.418(5) cm⁻¹.     

Fourier transform emission spectroscopy of YbO in the near-infrared region

The emission spectrum of gas-phase YbO has been investigated using a Fourier transform spectrometer. Chemiluminescence was observed from excited YbO molecules produced in a Broida-type oven by the reaction of ytterbium metal vapor with N₂O. A total of eight red-degraded bands in the range 9800-11 300 cm⁻¹ were recorded at a resolution of 0.04 cm⁻¹. Because of the multiple isotopomers present in the spectra, only three bands were rotationally analyzed. Perturbations were identified in two of these bands and all three transitions were found to terminate at the X1Σ+ ground electronic state. The electronic configurations that give rise to the observed states are discussed and molecular parameters for all of the analyzed bands are reported.     

Fourier transform emission spectroscopy of the FΔ-XΦ system of TiF

The emission spectra of TiF have been reinvestigated in the 4200-15 000 cm⁻¹ region using the Fourier transform spectrometer associated with the National Solar Observatory at Kitt Peak. TiF was formed in a microwave discharge lamp operated with 2.5 Torr of He and a trace of TiF₄ vapor, and the spectra were recorded at a resolution of 0.02 cm⁻¹. The TiF bands observed in the 12 000-14 000 cm⁻¹ region have been assigned to a new transition, F⁴Δ-X⁴Φ. Each band consists of four sub-bands assigned as, ⁴Δ_1/2-⁴Φ_3/2, ⁴Δ_3/2-⁴Φ_5/2, ⁴Δ_5/2-⁴Φ_7/2, and ⁴Δ_7/2-⁴Φ_9/2. A rotational analysis of the 0-1, 0-0, and 1-0 bands has been obtained and spectroscopic constants have been extracted.     

Fourier transform spectroscopy of new emission systems of NbN in the visible region

The emission spectrum of NbN has been reinvestigated in the 8000-35 000  cm⁻¹ region using a Fourier transform spectrometer and two groups of new bands were observed. The bands observed in the 18 000-20 000 cm⁻¹ region have been assigned to a new ³Π-X³Δ transition. Three bands with R heads near 19 463.8, 19 659.0 and 19 757.0 cm⁻¹ have been assigned as 0-0 bands of the ³Π₂-X³Δ₃, ³Π₁-X³Δ₂ and ³Π_0±-X³Δ₁ subbands, respectively, of this new transition. Three additional ΔΩ = 0 bands have been observed in the 24 000-26 000  cm⁻¹ region. A 0-0 band with an R head near 25 409.9 cm⁻¹ has been assigned as a ΔΩ = 0 transition having X³Δ₂ as its lower state while two additional bands with heads near 25 518.7 and 25 534.8 cm⁻¹ were found to be ΔΩ = 0 bands having X³Δ₁ as the common lower state. Two of these three bands are perhaps subbands of a ³Δ-X³Δ transition. Most of the excited levels are affected by perturbations.     

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.     

Dispersive Fourier transform spectroscopy with gases in the visible region

The method of dispersive Fourier transform spectroscopy (DFTS) with gases in the visible wavenumber range is described in detail and compared with the method of scanning-wavelength interferometry (SWI). Measurements of the dispersion of the complex refractive index of gases can be performed successively in several minutes using the same apparatus and gas sample conditions for both methods. In the reported experiments with CH₄ a very simple mirror drive was used. Nevertheless, reasonable results are obtained for the dispersion of the real refractive index of CH₄ in the wavenumber range 16,000 ⩽ σ ⩽ 23,000 cm⁻¹.     

Fourier transform emission spectroscopy of some new bands of ReN

The emission spectrum of ReN has been reinvestigated in the visible region using a Fourier transform spectrometer. Two new bands have been identified with band origins near 22 110 and 22 224 cm⁻¹. These bands have a common lower state and have been assigned as the 0⁺–A1 and 0⁻–A1 transitions. After rotational analysis it was noted that the new 0⁺–A1 transition also has its upper state in common with the upper state of the [24.7]0⁺–X0⁺ transition reported previously [W.J. Balfour, J. Cao, C.X.W. Qian, S.J. Rixon, J. Mol. Spectrosc. 183 (1997) 113–118.]. This observation provides T₀₀ = 2616.26 cm⁻¹ for the A1 state. It is likely that the A1 and X0⁺ states are two spin components of the ³Σ⁻ ground state.     

Fourier transform emission spectroscopy: The vibration-rotation spectrum of CuH

The Fourier transform infrared emission spectrum of CuH was observed. The (1, 0), (2, 1), and (2, 0) vibration-rotation bands of both ⁶³CuH and ⁶⁵CuH were recorded from a copper hollow-cathode discharge in neon and hydrogen. Improved molecular constants for the v = 0, 1, and 2 levels of CuH are provided. This work is the first observation of a vibration-rotation spectrum of a metal hydride in emission.     

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.     

Microcomputers in Fourier transform spectroscopy

With the rapid advancement of VLSI technologies, microcomputer systems with relatively fast CPU processing time and electronic memory (RAM) of 1 Mbyte are now available at a reasonably low cost. We discuss the interfacing of microcomputers with 6502, 8086 and 68000 CPU to an FTS system. The performance of some A/D converters and microcomputer-controlled micropositioners available commercially are also discussed.     

The laser-induced fluorescence spectroscopy of TiF in the ultraviolet region

The laser-induced fluorescence (LIF) spectrum of jet-cooled ⁴⁸TiF has been obtained in the wavelength region of 245-270 nm for the first time. Six pairs of vibronic bands were observed and assigned to two new transitions [37.8]⁴Φ-X⁴Φ and ⁴Δ-X⁴Φ. Rotational analysis was carried out for the (ν′ = 0-3 to ν″ = 0) vibrational bands of the [37.8]⁴Φ_3/2-X⁴Φ_3/2 and [37.8]⁴Φ_5/2-X⁴Φ_5/2 subbands, and also, the (ν′, 0) and (ν′+1, 0) vibrational bands of the ⁴Δ_1/2-X⁴Φ_3/2 and ⁴Δ_3/2-X⁴Φ_5/2 subbands. The effective equilibrium molecular constants for the [37.8]⁴Φ_3/2 and [37.8]⁴Φ_3/2 upper states were determined. In addition, lifetime measurements were carried out for all of the observed bands under collision-free conditions. On the basis of the spectroscopic constants and lifetime measurements, the electronic transitions involved in the observed high-lying electronic states are discussed.     

Fourier transform spectroscopy of NbS

Emission bands attributed to the NbS radical have been observed in the near infrared and visible regions with FTS techniques using an electrodeless 2450 MHz discharge as a source. Transitions within the doublet and quartet manifolds were recorded at high resolution. The present paper gives the first rotational analysis of this molecule. Numerous bands within the doublet and quartet manifolds have been analyzed, resulting in the characterization of seven different electronic states, three in the doublet and four in the quartet manifold. The states have been labeled in analogy with NbO. The analyzed electronic states are: X⁴Σ⁻, C⁴Σ⁻, A′⁴Φ, D⁴Δ, a²Δ, c²Π, and e²Φ. Four additional substates in the doublet manifold have also been analyzed. In all, 27 vibrational sublevels have been included in the analysis, the total number of rotational lines being about 18 000. The positions of the analyzed transitions are: C⁴Σ⁻ → X⁴Σ⁻ near 15 670 cm⁻¹, D⁴Δ → A′⁴Φ near 7740 cm⁻¹, c²Π → a²Δ near 5850 cm⁻¹ and e²Φ → a²Δ near 8500 cm⁻¹. The overall picture is consistent with the corresponding analysis of NbO. However, three energy separations could not be derived from the experimental data in the case of NbS, i.e., the a²Δ− X⁴Σ⁻, A′⁴Φ− X⁴Σ⁻ and a²Δ_5/2-a²Δ_3/2 splittings. These were set to 4992, 5490, and 992 cm⁻¹, respectively, from preliminary ab initio calculations. In this way, a tentative energy level scheme could be drawn. The first order spin-orbit parameter of the A′⁴Φ state was indeterminable from the experimental data and was set to the value 170 cm⁻¹, derived from the same calculations.     

Fourier transform emission lifetime spectrometer

We report a rapid and low cost Fourier transform spectrometer that uses a path length modulated Michelson interferometer to simultaneously measure excitation spectra and excitation wavelength-dependent emission lifetimes. Excitation spectra and lifetimes of excited tris(2,2'-bipyridyl) ruthenium(II) measured using this technique corresponded to values known in the literature. Excitation-dependent lifetimes of porous silicon measured with this technique suggest the influence of quantum confinement effects. This method may be useful for measuring mixtures of emitting species with closely spaced lifetimes as well as studying excitation wavelength-dependent emission phenomena.     

Double-beam weighting in Fourier transform spectroscopy

This paper describes a double-beam weighting system in slow-scanning Fourier transform spectroscopy by use of a photo-conductive detector with fast response. It uses the method of amplitude modulation. The intensity of reference beam (A) and that of sample beam (B) are obtained by summing and subtracting the signals (A + B) and (A ? B), which are obtained in this form from a modulated signal by means of an electronic system. Merits arising from using a detector with fast response in double-beam weighting are also discussed. The operational performance of the system has been evaluated and it has been found that the spectra thus obtained are reproducible because they are kept within 3% bound and each measured value coincides with the averaged trace of single-beam measurements within ±2%.     

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.     

Fourier spectroscopy of the stratospheric emission

Emission spectra of the stratosphere have been recorded from balloon altitude with an unapodized resolution of 0.0033 cm^–1 in the submillimeter (SM) spectral range. Preliminary results on constituent identification are presented in this paper.     

Infrared Fourier transform spectroscopy of PH

The infrared vibration-rotation spectrum of the PH radical was observed in emission using a high-resolution Fourier transform spectrometer. The observation of five bands (1-0, 2-1, 3-2, 4-3, and 5-4) allowed the first six vibrational energy levels of the ground X³Σ⁻ state to be characterized. An RKR potential curve for the ground state was computed.     

Two-dimensional Fourier transform spectroscopy in the pump-probe geometry

Two-dimensional (2D) Fourier transform (FT) infrared spectroscopy is performed by using a collinear pulse-pair pump and probe geometry with conventional optics. Simultaneous collection of the third-order response and pulse-pair timing permit automated phasing and rapid acquisition of 2D absorptive spectra. To demonstrate the ability of this method to capture molecular dynamics, couplings and structure found in the conventional boxcar 2D FT spectroscopy, a series of 2D spectra of a metal carbonyl, and a beta-sheet protein are acquired.