Spectroscopy of AlO: Combined analysis of the AΠi → XΣ and BΣ → XΣ transitions

A combined analysis of the A²Π_i → X²Σ⁺ and B²Σ⁺ → X²Σ⁺ band systems of AlO, involving 21,500 line assignments, has been performed. The analysis indicates that the previously reported γ values of the B²Σ⁺ state are questionable. The present analysis shows that γ(B²Σ⁺) ≈ 0.014 cm⁻¹, essentially independent of the vibrational level. The positive sign is consistent with second order interaction with the higher-lying C²Π_r and lower-lying A²Π_i states. It also appears that many of the previously reported γ and γ_D values of X²Σ⁺ (v > 0) are doubtful. In fact, γ(X²Σ⁺) is observed to become increasingly negative for v″ > 1, due to second order interaction with the low-lying A²Π_i state. The present results are based on models where the hyperfine structure of the ²Σ⁺ states has been taken into account explicitly. Intensity patterns of the branches of the B²Σ⁺ → X²Σ⁺ system have been shown to be influenced by the case bβ_S coupling in the ground state v = 0,1 levels. This gives rise to intensity differences of around 10 percent in the R₁/R₂ and P₁/P₂ doublet components. The synthesized intensity patterns are fully in accord with the F₁/F₂ assignments of the present work.     

Doppler-limited spectroscopy of the AΠ1 ← XΣ system of ICl in the 0.8 μm region using a Ti:sapphire ring laser

Doppler-limited vib-rotational absorption spectra of the A ← X electronic transition of I^35/37Cl are measured in the range 11,352-13,507 cm⁻¹ using a Ti:sapphire ring laser. The P-, Q-, and R-branch lines belonging to the v ← v″ = (0-7) ← (0-7) transition in I³⁵Cl and the v ← v″ = (0-6) ← (2-6) transition in I³⁷Cl are assigned. Under Doppler-limited conditions, the P- and R-branch lines are split into doublets by the nuclear quadrupole coupling effect of the I atom. The unperturbed positions of these lines are correctly calculated, whereas splitting in the Q-branch lines was not observed. The mass-reduced Dunham expansion coefficients U_l,m of the A and X states and the spectroscopic constants , and H_v^′ of the A state are determined using a global least-squares fitting procedure.     

Rotational analysis of the (3, 6) band in the comet-tail (AΠi -XΣ) system of CO

The direct observation and rotational analysis of the (3, 6) band in the comet-tail (A²Π_i-X²Σ⁺) system of CO⁺ are carried out for the first time employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. That 193 lines are assigned to this band ranging from 12 100 to 12 370 cm⁻¹ results in most accurate molecular constants by nonlinear least-squares fitting procedure employing the effective Hamiltonians.     

New spectroscopic investigations of the fourth-positive (AΠ → XΣ) system bands in the CO molecule

The present work puts forward the results of the recordings carried out under high resolution by conventional, photographic spectroscopy and modern analysis of thirteen bands with v′ = 7-12 and v″ = 16-24 of the fourth-positive (A¹Π → X¹Σ⁺) band system. The current investigations include the region of the observed ¹³C¹⁶O molecule spectrum, much greater now than before. Especially, new transitions connected with not hitherto observed v′ = 12 vibrational level of the A¹Π state, were recorded and studied. Moreover, the region of perturbations observed in the upper state of the fourth-positive system was significantly enlarged. The observed perturbations were confronted with those predicted from theoretical calculations.     

Fourier transform spectroscopy of chemiluminescence from the AΠ-XΣ system of SrO

The A^′1Π-X¹Σ⁺ near infrared system of strontium oxide (SrO) was observed at high spectral resolution by measuring the chemiluminescence from a Broida flow reactor using a Fourier transform spectrometer. In total, 32 bands from , , were measured within the spectral region at a resolution of . Vibrational levels of the upper state were observed up to v_A^′=4, and more than 5600 rotational lines were assigned. Incorporating previously published high resolution data for the A¹Σ⁺-X¹Σ⁺ system, a global fit to both data sets yields improved Dunham constants for the ground state and for the lower vibrational levels (v_A^′=0, 1, and 2) of the A^′1Π state. Because perturbations arising from interactions with the b³Σ⁺ and A¹Σ⁺ states affect the higher vibrational levels of the A^′1Π state more strongly, levels v_A^′=3 and 4 were represented by effective band constants in the fits. RKR potentials for the X¹Σ⁺,A^′1Π, and b³Σ⁺ states have been generated utilizing all the available data, Franck-Condon factors have been calculated for the A^′1Π-X¹Σ⁺ system, and A^′1Π∼b³Σ⁺ and A^′1Π∼A¹Σ⁺ perturbations are discussed.     

High-resolution Fourier transform emission spectroscopy of the AΠ-XΣ system of GeSe

Natural germanium and selenium consist of, respectively, five and six stable isotopes. Several of these isotopes have considerable abundances and one should expect to observe the bands of at least six isotopic variants of germanium monoselenide (GeSe). In this paper, for the first time, the results of the high-resolution electronic spectrum of the main transition A¹Π-X¹Σ⁺ of the specific isotopomer ⁷⁴Ge⁸⁰Se, excited in a microwave discharge and recorded in the 33 500-26 000 cm⁻¹ region using a Fourier transform spectrometer, is discussed. From the rotational analysis of 25 bands involving v″ = 0-12 and v′ = 0-7, accurate vibrational and rotational constants of the A¹Π state are determined. The present study has revealed perturbations in the v′ = 6 and 7 levels of the A¹Π state.     

The 1-v″ bands progression of the BΣ → XΣ system of CO

The B²Σ⁺ → X²Σ⁺ (0-1, 2, 3, 4 progression) electronic transition of ¹²C¹⁷O⁺ was first observed and analyzed by Szajna and Ke¸pa [Spectrochim. Acta A 65 (2006) 1014-1020]. We have now extended our previous studies. The use of high resolution conventional spectroscopic techniques has allowed first rotational analysis of the 1-2, 1-3, 1-4 and 1-5 bands of the first negative system in the 37,000-43,000 cm⁻¹ spectral region. Approximately 500 transition wavenumbers were measured with an estimated accuracy of 0.005 cm⁻¹. The present data were combined with the previous measurements to yield an improved set of molecular constants for the B²Σ⁺(v′ = 0, 1) and X²Σ⁺(v″ = 1, 2, 3, 4, 5). The v′ = 1 and v″ = 5 vibrational levels were observed for the first time and the main molecular constants are (in cm⁻¹, one standard deviation in parentheses)

B2Σ+		X2Σ+
B1 = 1.710792(20)		B5 = 1.825694(23)
D1 = 7.799(15) × 10−6		D5 = 6.085(21) × 10−6
γ1 = 1.9491(37) × 10−2		γ5 = [8.381] × 10−3

Full-size table

     

Absorption spectrum of the (2, 1) band in the AПi-XΣ system of CS cation

The spectrum of CS⁺ cation was recorded in the 12,235-12,600 cm⁻¹ region by employing optical heterodyne velocity modulation absorption spectroscopy. In combination with simultaneous measurement of optical heterodyne concentration modulation absorption spectroscopy, the spectral lines of CS⁺ blended with the neutral CS lines were identified and extracted from the observed spectra. One hundred and eighty-two spectral lines of CS⁺ were assigned to the (2, 1) band in the A²П_i-X²Σ⁺ system and the improved molecular constants of the upper level (υ = 2) in the A²П_i state were derived by nonlinear least squares fitting.     

Ab initio study of the spectroscopy of the XΠ electronic ground states of CNO and NCO

The X²Π electronic ground states of NCO and CNO have been investigated by complete ab initio methods. The dependence of the Renner-Teller parameters, ? and , on the ab initio method and on the basis set have been studied. These parameters have also been compared to experimental data for NCO. The potential energy surfaces of the X²Π state have been determined by the MRCI method and the cc-pVQZ basis set for NCO and CNO. The rovibronic levels of both isomers have been calculated variationally up to approximatively 4000 cm⁻¹ for J ? 5/2 and K ? 2, with the inclusion of the geometry dependence of the spin-orbit coupling. The agreement with experimental data obtained for NCO is remarkable. A similar accuracy for the ab initio rovibronic levels of CNO is expected since no experimental data exists for this isomer.     

The far-infrared and microwave spectra of the CH radical in the v = 1 level of the XΠ state

Transitions between the spin-rotational levels of the ¹²CH radical in the v = 1 level of the X²Π state have been studied by the technique of laser magnetic resonance at far-infrared wavelengths. The data have been combined with a measurement of lambda-doubling transition frequencies at 7 GHz to determine an improved set of molecular parameters for CH in the v = 1 level. The parameters provide information on the effects of vibrational excitation on the structural properties of CH. Accurate predictions of the transition frequencies between the low-lying levels of the radical in the absence of a magnetic field have also been made.Small inconsistencies in the least-squares fit of the laser magnetic resonance data prompted re-measurement of three far-infrared laser frequencies, the 122.5 μm line of CH₂F₂ pumped by 9R(22), the 122.5 μm line of CH₂F₂ pumped by 9P(8) and the 554.4 μm line of CH₂CF₂ pumped by 10P(14). The new measurements differ by as much as 3.8 MHz from those made previously and are more accurate; they also remove the inconsistencies in the fit. The re-measured frequencies of the two 122.5 μm lines are identical within experimental error which suggests that the far-infrared lasing transition is the same, namely the ^rR₂₃(32) transition in the v₉=1 level of CH₂F₂.     

Laser spectroscopy of VS: hyperfine and rotational structure of the CΣ-XΣ transition

The (0,0) and (0,1) bands of the C⁴Σ⁻-X⁴Σ⁻ electronic transition of VS (near 809 and 846 nm, respectively) have been recorded at high resolution by laser-induced fluorescence, following the reaction of laser-ablated vanadium atoms with CS₂ under supersonic free-jet conditions. A least squares fit to the resolved hyperfine components of the rotational lines gives the rotational constants and bond lengths as C⁴Σ⁻: , ; X⁴Σ⁻: , . The electron spin parameters for the two states show that there are some similarities between the states of VS and those of VO, but the hyperfine parameters show that the compositions of the partly filled molecular orbitals are by no means the same. The ground state Fermi contact parameter of VS, b(X⁴Σ⁻), is only 58% of that of the ground state of VO, which implies that the σ orbital of the ground σδ² electron configuration has less than 50% vanadium 4s character. Similarly, the excited state Fermi contact parameter, b(C⁴Σ⁻), is very much smaller than that of VO. No local rotational perturbations have been found in the C⁴Σ⁻ state of VS, though an internal hyperfine perturbation between the F₂ and F₃ electron components at low N confuses the hyperfine structure and induces some forbidden (ΔJ=±2) rotational branches.     

An ab Initio Study of the ÃΠ State and the ÃΠ←X?Σ Electronic Transition of MgNC

We use the RENNER program system (see, for example, P. Jensen, G. Osmann, and P. R. Bunker, in “Computational Molecular Spectroscopy” (P. Jensen and P. R. Bunker, Eds.), Wiley, Chichester, 2000, and references therein) to make a detailed calculation of the rovibronic energies in the first excited electronic state, òΠ, of the MgNC radical. This calculation is based on ab initio data (supplemented here with points for larger bending displacements from linearity) calculated at the level of MR-SDCI(+Q)/[TZ3P+f(Mg), aug-cc-pVQZ (N and C)] by T. E. Odaka, T. Taketsugu, T. Hirano, and U. Nagashima (J. Chem. Phys.115, 1349-1354 (2001)). These authors employed ab initio derived spectroscopic constants to calculate vibronic energies using perturbation expressions (J. T. Hougen and J. P. Jesson, J. Chem. Phys.38, 1524-1525 (1963)), and their results suggested that an observed vibronic band belonging to the òΠ←X?²Σ⁺ electronic transition (R. R. Wright and T. A. Miller, J. Mol. Spectrosc.194, 219-228 (1999)) should be reassigned. The present work confirms this conclusion, which is further substantiated by the rotational structures calculated in the vibronic states and by Franck-Condon theory predicting relative intensities.     

High-resolution Fourier-transform study of the X2Π3/2 → X1Π1/2 fine structure transitions of PbH and PbD

Near-infrared emission spectra of the X₂²Π_3/2 → X₁²Π_1/2 fine structure transitions of PbH and PbD have been investigated by high-resolution Fourier-transform spectrometry. The fine structure splitting in the X²Π_r ground state of ²⁰⁸PbH was found to be 6924.4926(4) cm⁻¹. Accurate rotational constants for the v = 0 and 1 vibrational levels of the X²Π_r states of ²⁰⁸PbH, ²⁰⁷PbH, ²⁰⁸PbD and ²⁰⁷PbD and hyperfine structure constants for the X₁²Π_1/2 states of ²⁰⁷PbH (²⁰⁷PbD) have been derived.     

Intracavity laser absorption spectroscopy of AuO: Identification of the BΣ-XΠ3/2 transition

The visible electronic spectrum of AuO has been recorded at rotational resolution using intracavity laser absorption spectroscopy. Six vibrational bandheads have been identified, and three of the bands have been analyzed and assigned as bands of a newly identified B²Σ⁻-X²Π_3/2 transition of AuO. The molecular parameters for the newly identified B²Σ⁻ state are presented.     

Laser spectroscopy of CuS: Analysis of the A2Σ-X2Πi system

Laser excitation spectra of the A²Σ-X²Π_i system have been recorded for ⁶³CuS and ⁶⁵CuS isotopic molecules with a single-mode dye laser operating in the region 17000–18000 cm^?1. For highly overlapped sequences, use of a monochromator as a narrow band filter was necessary to allow rotational analysis. A simultaneous fit of all eight analyzed bands has led to the following spectroscopic constants for ⁶³CuS (in cm^?1):

     

17.

Rovibrational spectroscopy of the Fermi-interacting ν₄ = 1 and ν₃ = ν₆ = 1 levels of DCF₃     

Petr Pracna  Adina Ceausu-Velcescu  Štěpán Urban 《Journal of Molecular Spectroscopy》2010,259(1):1-10

The high-resolution infrared spectrum of deuterated fluoroform (DCF₃) was studied in the 700 and 1200 cm⁻¹ regions, with the aim of assigning and analyzing the ν₄ CF₃ asymmetric stretching vibration. The Fermi-type anharmonic coupling between the ν₄ = 1 and ν₃ = ν₆ = 1 rovibrational levels, already mentioned in an early work of Ruoff et al. [Spectrochimica Acta Part A 31A (1975) 1099-1100], was studied here for the first time under high resolution. Assignments in the ν₃ + ν₆/ν₄ band system were confirmed and extended by the identification of the ν₃ + ν₆ − ν₆ and ν₄-ν₆ bands in the 700 cm⁻¹ region, the latter being enhanced near the Fermi crossings of the studied levels. Data from both the hot and difference bands were included in the analysis. The close separation of the studied vibrational levels of about 14.8 cm⁻¹ produces a large variety of resonance crossings which involve levels with . Besides the Fermi () and Coriolis () resonances, they were accounted for by inclusion of additional higher-order ( and ) interaction terms between the vibrational states. The least-squares fit of more that 16,000 vibration-rotation transitions provides a quantitative reproduction of data in all bands.     

18.

Diode laser spectroscopy of the BO2 radical: The κ2Σ ← 2Π32 transition of the ν2 fundamental band     

《Journal of Molecular Spectroscopy》1986,116(2):450-457

     

19.

High-resolution emission spectroscopy of the AΠ–XΣ system of AlH     

Wojciech Szajna  Miros?aw Zachwieja 《Journal of Molecular Spectroscopy》2011,269(1):56-60

The emission spectrum of the A²Π–X²Σ⁺ system of the AlH⁺ ion was investigated in the range of 27 000–29 000 cm⁻¹ by using a conventional spectroscopic technique. The AlH⁺ molecules were formed and excited in an aluminium hollow-cathode lamp with two anodes, filled with a mixture of Ne carried gas and a trace of NH₃. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. The full rotational structure of the 0-0 and 1-1 bands has been observed for the first time (12 branches up to J″ = 36.5) and many new constants of the X²Σ⁺ state have been derived from the analysis. For the A²Π, v = 0 and 1 state a considerable irregularities of the Λ-doubling have been observed. The most reasonable explanation for this anomaly is an interaction with unstableness rotational levels of X²Σ⁺ state and perturbing of the A²Π state by the nearly lyingB²Σ⁺ state.     

20.

Catalysis of the hydrogen oxidation reactions by Sr-doped LaMn_1 − yCr_yO_3 ± δ oxides     

L. DeleebeeckV. Birss 《Solid State Ionics》2011,203(1):69-79

Sr-doped and Sr-free La_1 − xSr_xMn_1 − yCr_yO_3 ± δ (LSMC, x(Sr) = 0-0.2, y(Cr) = 0.4-0.6) perovskite-type oxides were synthesized and evaluated as single phase anodes for use in intermediate temperature solid oxide fuel cell applications. Their thermo-chemical and chemical stabilities were investigated in hydrogen at high temperatures and correlated with their oxygen non-stoichiometry (3 ± δ), determined by permanganate titration. The catalytic activity towards hydrogen oxidation was examined as a function of oxide sintering time, operating temperature, and the Sr and Cr contents, using a Pt mesh current collector. While all of the perovskite oxides studied here showed some irreversible performance degradation with time under both open circuit and anodically polarized conditions, La_0.9Sr_0.1Mn_0.6Cr_0.4O_3.03 (LSMC9164), sintered at 1200 °C for 10 h, was found to be the most catalytically active and also the most stable.     

State	$\text{v}$	$\text{T}{}_{\mathrm{v}}$	$\text{B}{}_{\mathrm{v}}$	$\text{D}{}_{\mathrm{v}}\text{× 10}{}^6$	$\text{γ}{}_{\mathrm{v}}$	$\text{p}{}_{\mathrm{v}}$	$\text{a}{}_{\mathrm{v}}\text{× 10}{}^6$
$\text{A}{}^2\text{Σ}{}^{\mathrm{?}}$	0	17924.335 (7)	0.17989 (4)	0.177 (7)	0.03853 (7)
$\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$	1	842.574 (7)	0.18701 (4)	0.163 (7)		0.01496 (9)
	0	432.566 (6)	0.18818 (4)	0.162 (7)		0.01508 (9)
$\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$	1	411.289 (7)	0.18724 (4)	0.184 (7)			?0.96 (6)
	0	—	0.18839 (4)	0.160 (7)			?0.11 (6)

Rovibrational spectroscopy of the Fermi-interacting ν4 = 1 and ν3 = ν6 = 1 levels of DCF3

The high-resolution infrared spectrum of deuterated fluoroform (DCF₃) was studied in the 700 and 1200 cm⁻¹ regions, with the aim of assigning and analyzing the ν₄ CF₃ asymmetric stretching vibration. The Fermi-type anharmonic coupling between the ν₄ = 1 and ν₃ = ν₆ = 1 rovibrational levels, already mentioned in an early work of Ruoff et al. [Spectrochimica Acta Part A 31A (1975) 1099-1100], was studied here for the first time under high resolution. Assignments in the ν₃ + ν₆/ν₄ band system were confirmed and extended by the identification of the ν₃ + ν₆ − ν₆ and ν₄-ν₆ bands in the 700 cm⁻¹ region, the latter being enhanced near the Fermi crossings of the studied levels. Data from both the hot and difference bands were included in the analysis. The close separation of the studied vibrational levels of about 14.8 cm⁻¹ produces a large variety of resonance crossings which involve levels with . Besides the Fermi () and Coriolis () resonances, they were accounted for by inclusion of additional higher-order ( and ) interaction terms between the vibrational states. The least-squares fit of more that 16,000 vibration-rotation transitions provides a quantitative reproduction of data in all bands.     

High-resolution emission spectroscopy of the AΠ–XΣ system of AlH

The emission spectrum of the A²Π–X²Σ⁺ system of the AlH⁺ ion was investigated in the range of 27 000–29 000 cm⁻¹ by using a conventional spectroscopic technique. The AlH⁺ molecules were formed and excited in an aluminium hollow-cathode lamp with two anodes, filled with a mixture of Ne carried gas and a trace of NH₃. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. The full rotational structure of the 0-0 and 1-1 bands has been observed for the first time (12 branches up to J″ = 36.5) and many new constants of the X²Σ⁺ state have been derived from the analysis. For the A²Π, v = 0 and 1 state a considerable irregularities of the Λ-doubling have been observed. The most reasonable explanation for this anomaly is an interaction with unstableness rotational levels of X²Σ⁺ state and perturbing of the A²Π state by the nearly lyingB²Σ⁺ state.     

Catalysis of the hydrogen oxidation reactions by Sr-doped LaMn1 − yCryO3 ± δ oxides

Sr-doped and Sr-free La_1 − xSr_xMn_1 − yCr_yO_3 ± δ (LSMC, x(Sr) = 0-0.2, y(Cr) = 0.4-0.6) perovskite-type oxides were synthesized and evaluated as single phase anodes for use in intermediate temperature solid oxide fuel cell applications. Their thermo-chemical and chemical stabilities were investigated in hydrogen at high temperatures and correlated with their oxygen non-stoichiometry (3 ± δ), determined by permanganate titration. The catalytic activity towards hydrogen oxidation was examined as a function of oxide sintering time, operating temperature, and the Sr and Cr contents, using a Pt mesh current collector. While all of the perovskite oxides studied here showed some irreversible performance degradation with time under both open circuit and anodically polarized conditions, La_0.9Sr_0.1Mn_0.6Cr_0.4O_3.03 (LSMC9164), sintered at 1200 °C for 10 h, was found to be the most catalytically active and also the most stable.