The ultraviolet absorption spectra of GeO in rare gas matrices

The absorption spectra of GeO isolated in rare gas matrices have been investigated in the wavelength region 1150–3000 Å using the 2.5-GeV synchrotron in Bonn as a continuum light source. Two vibrational progressions of bands have been found in each of the matrices, in neon, argon, krypton, and xenon. These progressions are situated in the regions 2400–2700 and 1800–2100 Å. They have been analyzed as corresponding to gas-phase bands of the A¹Π-X¹Σ⁺ and the E¹Σ⁺-X¹Σ⁺ systems, respectively. Absorption lines of matrix-isolated GeO were also found in the region 1180–1500 Å.     

TheB 2Σ-X 2Σ system of the CaF molecule

The spectrum of theB ²Σ-X ²Σ system of the CaF molecule has been photographed in the second order of a 10.6 m concave grating spectrograph with 0.33 Å/mm dispersion. The rotational structure of the (0, 0) and (1, 0) bands has been analysed and the precise molecular constants have been obtained. Using the constants so determined the band origins of a large number of bands with 0 <v′,v″ < 10 have been calculated and used to obtain the accurate vibrational constants forB andX states and these are presented.     

Extension of the A1Σ+-X1Σ+ system of7LiH near the dissociation limit

The absorption spectra of⁷LiH have been photographed in the 3,500?2,900 Å region using the second order of a 3.4 M Ebert spectrograph. Observations comprise previously observedA ¹ Σ ⁺-X ¹ Σ ⁺ transitions and several new vibrational bands of this system near the ionisation limit. Rotational and vibrational analysis of these bands (16≦V′≦20) have been carried out and the rotational constants for the upper states have been determined.     

New spectroscopic analyses and potential energy curves for the X1Σ+ and A1Σ+ states of NaH

The emission spectrum of NaH has been photographed in the ～6000–7300-Å region. Additional bands of the A¹Σ⁺ electronic transition have been analyzed and in particular the observed vibrational structure of the excited A state has been extended down to v′ = 0. New spectroscopic constants have been obtained, the v′ = 0 data leading to especially large changes in the constants of the anomalous A¹Σ⁺ state. New Rydberg-Klein-Rees (RKR) potential energy curves have been calculated up to v″ = 8 of the X¹Σ⁺ state and up to v′ = 20 in the A¹Σ⁺ state.     

A Reanalysis of theA1Π–X1Σ+Transition of AlBr

TheA¹Π–X¹Σ⁺transition of aluminum monobromide (AlBr) near 2800 Å was recorded using a Bruker IFS 120 HR Fourier transform spectrometer at nominal resolutions of 4 and 0.03 cm⁻¹. All bands showP,Q, andRbranches and all are degraded to longer wavelengths. The 0–0 band is the most intense and the Δv= 0 sequence dominates the observed spectrum. Each band appears doubled due to the natural isotopic abundances of⁷⁹Br (50.69%) and⁸¹Br (49.31%). Band origin shifts due to isotopic substitution of bromine were examined to confirm the assignments of isotopic species. The rotational structure of the 0–1, 1–2, 0–0, 1–1, and 2–2 bands was assigned and fitted. These data were merged with previously reported photographic data for the 1–0, 2–1, 3–2, 2–0, and 3–1 bands and also infrared and microwave measurements to provide an improved set of constants for both electronic states. The rotational constants for each vibrational level in theX¹Σ⁺state vary smoothly with increasing vibrational quantum number and thus an expansion of the constants in terms of equilibrium values is recommended. An expansion of theA¹Π rotational constants in terms of equilibrium values is not recommended as the distortion constants do not change smoothly with increasing vibrational quantum number. Therefore, the rotational constants for theA¹Π state were determined for each individual vibrational level. This approach leads to vastly improved vibrational constants for theA¹Π state by reducing correlations between rotational and vibrational constants. This problem is serious for theA¹Π state owing to severe departures from harmonic behavior in thev= 2 andv= 3 levels.     

Emission spectrum of MgCl molecule in 5030-4380Å

The emission spectrum of diatomic magnesium chloride molecule has been reinvestigated in the region 5030-4380 Å (B ²Σ⁺ —A ²Π transition) at a higher dispersion. The vibrational assignments of the bands are confirmed by observing the vibrational isotope shifts due to isotopes of magnesium and chlorine. Precise values of the vibrational constants are determined for theB ²Σ⁺ state.     

Fourier transform emission spectroscopy of the BΣ-XΣ system of CN

The emission spectrum of the B²Σ⁺-X²Σ⁺ system of CN has been observed at high-resolution using a Fourier transform spectrometer. The rotational structure of a large number of bands involving vibrational levels v = 0-15 of both electronic states has been analyzed, and improved spectroscopic constants have been determined by combining the microwave and infrared measurements from previous studies. Improved spectroscopic constants for vibrational levels up to v″ = 18 in the X²Σ⁺ state and v′ = 19 in the B²Σ⁺ state have been determined by combining the measurements of the 16-13, 18-17, 18-18, 19-15, and 19-18 bands of Douglas and Routly [Astrophys. J. Suppl. 1 (1955) 295-318] and 17-14 and 17-16 bands of Ito et al. [J. Chem. Phys. 96 (1992) 4195] with our data. The band constants obtained have been used to estimate equilibrium ground state constants for CN.     

The 1Σ+-X1Σ+ transition of the PN molecule

The recently observed ¹Σ⁺-X¹Σ⁺ transition of the PN molecule (J. Phys. B.13, 2251–2254 (1980)) has been photographed at high dispersion in the 1600–1900-Å region. A rotational analysis is carried out and shows 11 vibrational levels of the new ¹Σ⁺ state. These levels are perturbed and absolute vibrational numbering cannot be determined. Some perturbations can be accounted for by interactions with the A¹Π state. Weakening of lines are explained as accidental predissociations and allow us to discuss the dissociation energies of the X¹Σ⁺ and A¹Π states.     

The laser-induced fluorescence of IBr79

Four fluorescence progressions of the B0⁺-X¹Σ⁺ band of IBr⁷⁹ excited by a single-mode cw dye-laser have been observed and analyzed. Discrepancies in the reported rotational constants of the ¹Σ⁺ state have been resolved and improved vibrational constants determined. A simple method of discriminating between IBr and interfering I₂ fluorescence is described.     

Studies on the Vibrational and Rovibrational Energies and Vibrational Force Constants of Diatomic Molecular States Using Algebraic and Variational Methods

Alternative expressions for vibrational and rotational spectrum constants and energies of diatomic molecular electronic states based on perturbation theory are suggested. An algebraic method (AM) is proposed to generate a converged full vibrational spectrum from limited energy data, and a potential variational method (PVM) is suggested to produce the vibrational force constants f_n and rotational spectrum constants using the perturbation formulae and the AM vibrational constants. The AM and PVM have been applied to study 10 diatomic electronic states: the X¹Σ_g⁺ and C¹Π_u⁻ states of H₂; the X¹Σ_g⁺, A³Σ_u⁺, B′³Σ_u⁻, and B³Π_g states of N₂; the X³Σ_g⁻, A³Σ_u⁺, and c¹Σ_u⁻ states of O₂; and the X¹Σ_g⁺ state of Br₂. Calculations show that (1) the AM E_υmax converges to the correct molecular dissociation energy; (2) the AM not only reproduce the input energies, but also generate the E_υ's of high vibrational excited states which may be difficult to obtain experimentally or theoretically; (3) the PVM vibrational force constants f_n may be used to measure the relative chemical bondstrengths of different diatomic electronic states for a molecule quantitatively.     

Rotational analysis of the a3Π-X1Σ+ bands of GaD

A new method of producing strong and clean emission spectra of the gallium hydride/deuteride molecule has been developed. Five bands belonging to the gallium deuteride molecule (GaD) have been photographed under high resolution. The rotational analyses of the bands lying at 5669.14 Å (0-0) and 5675.10 Å (1-1) in the a³Π₁-X¹Σ⁺ transition, 5761.0 Å (0-0) and 5766.20 Å (1-1) in the a³Π_0⁺-X¹Σ⁺ transition, and 5760.85 Å (0-0) in the a³Π_0⁻-X¹Σ⁺ transition have been performed. Accurate rotational constants (B, D) have been determined for the X¹Σ⁺, a³Π_0^± and a³Π_1^± states. The Λ doubling in the a³Π₀ (v = 0) and a³Π₁ (v = 0 and 1) states are obtained.     

The RKR potential energy curves for the X1Σ+ and A1Σ+ states of RbH

The A¹Σ⁺-X¹Σ⁺ laser-excited fluorescence spectrum of RbH was observed in the 4760-to 8470-Å region, using the Ar⁺ 4765-Å exciting line, and v″ = 6–12 were observed for the first time. New spectroscopic constants were obtained for the X¹Σ⁺ and A¹Σ⁺ states of RbH. New Rydberg-Klein-Rees (RKR) potential energy curves were calculated up to v″ = 12 of the X¹Σ⁺ state and up to v′ = 14 of the A¹Σ⁺ state.     

Reexamination of the vacuum ultraviolet emission spectrum of CO in the 950–1200 Å region

New spectrograms of CO below 1200 Å reveal that emission bands terminating on the high energy $\text{E}{}_0{}^1\text{Σ}{}^{\mathrm{+}}$ and ¹Π states plus most of the previously reported unidentified emission bands of CO actually originate from molecular nitrogen. Four new emission band systems in CO, tentatively identified as V¹Π-X¹Σ⁺, W¹Π-X¹Σ⁺, Y¹Σ⁺-X¹Σ⁺, and Z¹Σ⁺-X¹Σ⁺, have been observed. The corresponding T_v0′s are 98917, 102804, 99963, and 105724 cm^?1, respectively.     

Continuous wave optically pumped iodine laser: Spectroscopy and long range analysis of the X1Σg+ ground state of I2

Continuous wave oscillation is observed on transitions belonging to the I₂B 0_u⁺-X¹Σ_g⁺ system into highly excited vibrational levels of the ground state. The I₂ laser is optically pumped with a single longitudinal mode argon ion laser oscillating at either 514.5 or 501.7 nm resulting in some 752 assigned laser lines throughout the visible and near infrared. Of these, 44 transitions have 83 ≤ v″ ≤ 96 and are used here to obtain rotational and vibrational constants for levels of X¹Σ_g⁺ near the dissociation limit. A long range analysis applying the theory of LeRoy to the highest observed levels yields C₆ = 1.1 ± 0.1 × 10⁶ cm^?1 Å^?6 and indicates that the last bound vibrational level of X¹Σ_g⁺ has v = 114.     

Transition Probabilities in the BΣ-XΣ and the BΣ-AΠ Electronic Systems of MgO

Transition probabilities for the B¹Σ⁺-X¹Σ⁺ and the B¹Σ⁺-A¹Π electronic systems are presented for v=0-4 and J=0-150 in each electronic state. The functional form of the electronic transition moment for the B-X transition is taken from published ab initio results. The B-A moment is assumed to have the same form and is scaled using empirical branching ratio data. The R_e(r) are used with Rydberg-Klein-Rees (RKR) wavefunctions to calculate transition probabilities for v=0-4 and J=0-150. The RKR potentials were calculated based on empirical spectroscopic constants.     

A photoelectron spectroscopic study of the second ionisation of the CF(X2Π) radical

The CF(X²Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF⁺(X¹Σ⁺)←CF(X²Π) and CF⁺(a³Π)← CF(X²Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ω_e and r_e to be determined as 1810±30 cm⁻¹ and 1.154±0.005 Å, respectively for the first ionic state, CF⁺(X¹Σ⁺), and 1614±30 cm⁻¹ and 1.213±0.005 Å, respectively for the second ionic state, CF⁺(a³Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.     

The Ångström (B1Σ+-A1Π) band system of the 14C18O molecule

The Ångström (B¹Σ⁺-A¹Π) band system of the ¹⁴C¹⁸O molecule has been excited and photographed. The derived vibrational and rotational constants (in cm⁻¹) are:     

Infrared and near infrared emission spectra of SbH and SbD

The X³Σ⁻ ground state vibration-rotation spectrum of SbH and the near infrared spectra of the b¹Σ⁺-X³Σ⁻ transitions of SbH and SbD have been measured at high resolution by Fourier transform spectroscopy. The SbH and SbD radicals were generated in a tube furnace with a D.C. discharge of a flowing mixture of argon, hydrogen (or deuterium), and antimony vapor. In the infrared region, the 1-0 and 2-1 bands of the three components (0⁺, 1_e, and 1_f) as well as the 0⁺ component of the 3-2 band were observed for ¹²¹SbH and ¹²³SbH. In the near infrared region, the 0-0, 1-1, and 2-2 bands of the b¹Σ⁺-X³Σ⁻ system of both SbH and SbD as well as the 3-3 band of SbD were observed. Except for a few lines, the antimony isotopic shift was not resolved for these electronic spectra. The present data set was combined with the available ground state data on SbD and a¹Δ data for SbH and SbD from previous work, and a least-squares fit was performed for each of the four isotopologues: ¹²¹SbH, ¹²³SbH, ¹²¹SbD, and ¹²³SbD. Improved spectroscopic constants were obtained for the observed vibrational levels of the X³Σ⁻, a¹Δ, and b¹Σ⁺ states of these four isotopologues. In addition, all the above data were also fitted simultaneously to a multi-isotopologue Dunham model, which yielded Dunham constants and Born-Oppenheimer breakdown parameters for these three electronic states. Interestingly, we found that Born-Oppenheimer breakdown corrections were also required for some of the spin-spin and spin-rotation parameters of the X³Σ⁻ state.     

High resolution Fourier transform spectrum of GaCl

The electronic emission spectrum of the A³Π₀-X¹Σ⁺ and B³Π₁-X¹Σ⁺ transitions of Gallium monochloride molecule (⁶⁹GaCl) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.035 cm⁻¹. The rotational structure of the 0-0, 1-0, 2-1, and 3-2, bands belonging to A-X and 0-0, 0-1, 1-2, and 0-2 bands belonging to B-X transitions has been analyzed and equilibrium rotational constants for the X¹Σ⁺ and A³Π₀ states have been obtained. For the first time we are able to determine the Λ-doubling constants in the v = 0 and 1 levels of the B³Π₁ state.     

Jet-cooled laser-induced fluorescence spectroscopy of B2Σ+–X2Σ+ system of scandium monoxide: Improved molecular constants at equilibrium

The investigation on B²Σ⁺–X²Σ⁺ system of ScO was extended to higher vibrational levels by laser-induced fluorescence (LIF) spectroscopy in a free-jet. We have observed rotationally resolved excitation spectra for (4,0), (3,0), (2,0), and (1,2) bands in addition to the previously observed (0,0) and (1,0) bands. The wavenumbers of these bands were fitted to a Hamiltonian matrix to determine the molecular constants for the vibrational levels up to ν′=4 of the B²Σ⁺ state and ν″=2 of the X²Σ⁺ state. In addition, the vibration constants of the ground states were determined from the dispersed fluorescence wavenumbers between B²Σ⁺ (ν′=0–4) and X²Σ⁺ (ν″=0–8) transitions. The equilibrium molecular constants, derived from the extensive set of molecular constants for individual vibrational levels, were used to construct RKR potential energy curves for both the electronic states. The Franck–Condon factors were also calculated for the B²Σ⁺–X²Σ⁺ transition.