The infrared part of the C2 Phillips system (2.3–0.9 μm)

Line positions and molecular constants for the 0-0, 1-0, 2-0, 0-1, 2-1, 3-1, 0-2, 1-2, and 4-2 bands of the C₂ Phillips system ($\text{A}{}^1\text{Π}{}_{\mathrm{u}}\text{-X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$) are reported. Among them, five bands have not been reported previously. Rotational perturbations have been observed in the previously unobserved v = 1 level of the $\text{A}{}^1\text{Π}{}_{\mathrm{u}}$ state. This state is perturbed by the $\text{c}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state which was discovered by Ballik and Ramsay. These observations provide new information regarding the perturbing state. In particular, the minimum of the potential energy for the $\text{c}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state has been found to be at 9227.4 cm^?1 instead of 13 310 cm^?1, which was the previous T_e value for this electronic state.     

Lifetime of electronic states of CO2+

The radiative lifetimes of the $\text{A}\text{?}{}^2\text{Π}{}_{\mathrm{u}}$ and $\text{B}\text{?}{}^2\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ states of CO₂⁺ were measured by means of the delayed coincidence method. Excitation was performed by a pulsed electron beam incident on CO₂. The results of these measurements are 115 ± 5 nsec for the $\text{A}\text{?}{}^2\text{Π}{}_{\mathrm{u}}$ state and 126 ± 3 nsec for the $\text{B}\text{?}{}^2\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state.     

The bending vibration bands ν4 and ν5 of HCCI

The bending vibration bands ν₄ and ν₅ of HCCI were studied. From the observed rotational structure the rotational constant B₀ and the centrifugal distortion constant D₀ were obtained. The results were B₀ = 0.105968(7) cm^?1 and D₀ = 1.96(7) × 10^?8 cm^?1 from ν₄ and B₀ = 0.105948(8) cm^?1 and D₀ = 1.96(11) × 10^?8 cm^?1 from ν₅. The structure of the hot bands 2ν₅(Δ) ← ν₅(Π) and 3ν₅(φ) ← 2ν₅(Δ) was also resolved and hence the values α₅ = ?3.033(8) × 10^?4 cm^?1 and q₅ = 9.3(3) × 10^?5 cm^?1 could be derived. The other most intense hot bands following ν₅ could be explained in terms of the Fermi diads $\text{ν}{}_3\text{2ν}{}_5{}^0$ and $\text{ν}{}_3\text{+}\text{ν}{}_5{}^{\mathrm{\pm 1}}\text{3ν}{}_5{}^{\mathrm{\pm 1}}$. Of the numerous hot bands accompanying ν₄, only those between different excited states of ν₄ could be assigned. Then estimates for α₄ and q₄ were also obtained. In addition, several vibrational constants were derived.     

Predissociation and Λ-doubling in the even-parity Rydberg states of the nitrogen molecule

Predissociations in the y¹Π_g and $\text{x}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ Rydberg states of N₂ (configurations $\text{1π}{}_{\mathrm{u}}{}^{\mathrm{?1}}\text{4pσ}$ and $\text{1π}{}_{\mathrm{u}}{}^{\mathrm{?1}}\text{3pπ}$, respectively) and their likely causes, are discussed. Peaking of rotational intensity at unusually low J values, without sharp breaking off, is interpreted as due to case c^? or case cⁱ predissociation. Λ doubling in the y state, attributed to interactions with the $\text{x}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state and with another, ¹Σ⁺, state of the same electron configuration as x, is analyzed. From this analysis the location of the (unobserved) ${}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ state, here labeled x′, is obtained. It is concluded that the predissociation in the Π⁺ levels of the y state is an indirect one mediated by the interaction with x′ coupled with predissociation of x′ by a ${}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state dissociating to ${}^4\text{S +}{}^2\text{P}$ atoms: combined, however, with perturbation of the y state by the k¹Π_g Rydberg state (configuration $\text{3σ}{}_{\mathrm{g}}{}^{\mathrm{?1}}\text{4dπ}$), whose Π⁺ levels are completely predissociated.     

Vibrational spectra and force constants of symmetric tops: High resolution spectra of monoisotopic H3SiCl in the 2200-cm−1 region and rovibrational analysis of the ν1 and ν4 fundamentals

The gas phase infrared spectra of monoisotopic H₃Si³⁵Cl and H₃Si³⁷Cl have been studied in the $\text{ν}{}_1\text{ν}{}_4$ region near 2200 cm^?1 with a resolution of 0.012 and 0.04 cm^?1, respectively, and rotational fine structure for ΔJ = ±1 branches has been resolved. In addition, some information on ν₃ + ν₄ of H₃Si³⁵Cl near 2750 cm^?1 has been obtained. ν₁ and ν₄ are weakly coupled by Coriolis x, y resonance, $\text{B}\text{Ω}{}_{14}\text{ζ}{}_{14}\text{～ 2 × 10}{}^{\mathrm{?3}}\text{cm}{}^{\mathrm{?1}}$, only the upper states K′ = 2, l = 0 and K′ = 1, l = ?1 being substantially affected. Local perturbation due to rotational l(±1, ±1)-type resonance with ν₃ + ν₅⁺¹ + ν₆⁺¹ and ν₃ + ν₅⁺¹ + ν₆^?1 is revealed in the ΔK = +1 and ?1 branches, respectively. From a fit of the experimental line positions, standard deviations of 1.4 and 3.8 × 10^?3 cm^?1, respectively, to a model with five interacting levels conventional excited state parameters and interaction constants have been obtained. In $\text{H}{}_3\text{Si}{}^{35}\text{Cl}\text{H}{}_3\text{Si}{}^{37}\text{Cl}$ the fundamentals are ν₁, $\text{2201.94380(15)}\text{2201.9345(7)}$ and ν₄, $\text{2209.63862(8)}\text{2209.6254(2)}\text{cm}{}^{\mathrm{?1}}$, respectively. Q branches of the “hot” band (ν₃ + ν₄) ? ν₃ and of ν₄ of the ²⁹Si and ³⁰Si species have been detected.     

High-resolution infrared spectrum of the ν2 and ν8 bands of CH2D2

A high-resolution infrared spectrum of methane-d₂ has been measured in the C-D stretching band region (2025–2435 cm^?1). Rotational structures of the ν₂ and ν₈ bands have been assigned by use of the ASSIGN-diagram method, and the c-type Coriolis interaction between ν₂ and ν₈ has been analyzed. The band origins, ν₂ = 2203.22 ± 0.01 cm^?1 and ν₈ = 2234.70 ± 0.01 cm^?1, the rotational constants and the centrifugal distortion constants for the two bands, and the Coriolis coupling constant, $\text{∥;ξ}{}_{28}{}^{\mathrm{c}}\text{∥; = 0.182 ± 0.015}\text{cm}{}^{\mathrm{?1}}$, have been determined.     

Analysis of the B′3Σu− → B3Πg (0,0) emission band of molecular nitrogen

The (0,0) band of the $\text{B′}\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{→ B}{}^3\text{Π}{}_{\mathrm{g}}$ emission (Infrared Afterglow) system of molecular nitrogen has been recorded with a resolution of 0.046 cm^?1 and a line position accuracy of 0.007 cm^?1. Six hundred and seventy-two lines are tabulated into a line list for the 1.53 μm (low-resolution) emission feature. Of these, 482 are assigned as members of the 27 branches of the B′ → B transition, while 150 are identified with the 1PG (3,6) band. Molecular constants for the v = 0 levels of the $\text{B′}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}$ and B³Π_g states have been computed and tabulated.     

3Σu−-3Σu+ coupling in the O2B3Σu− predissociation

The role of $\text{B}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{-2}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ spin-orbit mixing in the O₂ Schumann-Runge predissociation is investigated. The $\text{2}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state is found to cross the $\text{B}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}$ state near 2.0 Å with an interaction matrix element of approximately 55 cm^?1. This state contributes to the widths of the Bv ≥ 6 levels, but introduces only small level shift perturbations. When the partial widths due to the ${}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ interaction are added to the previously calculated widths due to the ⁵Π_u, ³Π_u, and ¹Π_u states, reasonable agreement is obtained with experimental measurements on O¹⁶O¹⁶ and O¹⁸O¹⁸. The possibility of non-Lorentzian line profiles and the dependence of the width on rotational quantum number is investigated. The approximation of the spin-orbit matrix element by its value at the crossing point is shown to be a good approximation for calculating the second difference perturbations.     

Energy levels of low lying triplet states of N2 from infrared emission studies

A theoretical model used to describe the $\text{B′}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}$ and B³Π_g states of N₂ is presented. Using recently acquired high resolution spectra of the $\text{B′}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{→ B}{}^3\text{Π}{}_{\mathrm{g}}$ (0-0) band, rotational energy levels of the v = 0 vibrational levels of these two states are generated with this model. These levels are in excellent agreement with those obtained using a combination differences technique. The precision of the model generated levels is 0.01 cm^?1. The previously unpublished rotational levels of Dieke and Heath for the $\text{A}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$, B³Π_g and C³Π_u states are referenced to the $\text{N}{}_2\text{X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ (v = 0, J = 0) ground level and tabulated here. Estimates of the precision of their work are made.     

Analysis of the Raman spectrum of SF6

The Raman active fundamentals ν₁(A1g), ν₂(Eg), ν₅(F2g), and the overtone 2ν₆ of SF₆ have been investigated with a higher resolution and the band origins were estimated to be: ν₁ = 774.53 cm^?1, ν₂ = 643.35 cm^?1, ν₅ = 523.5 cm^?1, and 2ν₆ = 693.8 cm^?1. Raman and infrared data have been combined for estimation of several anharmonicity constants. The ν₆ fundamental frequency is calculated as 347.0 cm^?1. From the analysis of the ν₂ Raman band, the following rotational constants of both the ground and upper states have been calculated:

$\text{B}{}_0\text{= 0.09111 ± 0.00005}\text{cm}{}^{\mathrm{?1}}\text{; D}{}_0\text{= (0.16±0.08)10}{}^{\mathrm{?7}}\text{cm}{}^{\mathrm{?1}}$

;

$\text{B}{}_2\text{= 0.09116 ± 0.00005}\text{cm}{}^{\mathrm{?1}}\text{; D}{}_2\text{= (0.18±0.04)10}{}^{\mathrm{?7}}\text{cm}{}^{\mathrm{?1}}$

.     

Analysis of the 2770-Å emission system in I2

A weak emission spectrum of I₂ near 2770 Å is reanalyzed and found to to minate on the A(1u³Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward $\text{I}{}^{\mathrm{?}}\text{(}{}^1\text{S) +}\text{I}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_1\text{)}$. In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″_e = 10 907 cm^?1, $\text{D}$″_e = 1640 cm^?1, ω″_e = 95 cm^?1, $\text{R″}{}_{\mathrm{e}}\text{= 3.06}\text{A}\text{?}$; T′_e = 47 559.1 cm^?1, ω′_e = 106.60 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.53}\text{A}\text{?}$.     

The emission spectra of H35Cl+, H37Cl+, D35Cl+, and D37Cl+ in the region 2700–4100 Å

The $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}\text{-X}{}^2\text{Π}$ emission spectrum of HCl⁺ has been measured and analyzed for four isotopic combinations. These analyses extend previous work and provide rotational constants for the v = 0–2 levels of the ground state and for the v = 0–9 levels of the excited state. RKR potentials have been determined for both states, although the upper state could not be fitted precisely to such a model. Calculated relative intensities based on these potentials demonstrated that the electronic transition moment must change rapidly with lower state vibrational quantum number. Although considerable caution should be exercised in applying the concept of equilibrium constants to the $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}$ state, the following are the best estimates of these constants (in cm^?1) for the $\text{X}{}^2\text{Π}$ state of H³⁵Cl⁺: B_e = 9.9406, ω_e = 2673.7, A_e = ? 643.7, and $\text{r}{}_{\mathrm{e}}\text{= 1.315}\text{A}\text{?}$. For the $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}$ state of H³⁵Cl: T_e = 28 628.08, B_e ～ 7.505, ω_e ～ 1606.5, and $\text{r}{}_{\mathrm{e}}\text{= 1.514}\text{A}\text{?}$.     

Intensity measurements and self-broadening coefficients in the γ band of O2 at 628 nm using intracavity laser-absorption spectroscopy (ICLAS)

Quantitative measurements of intensities and widths were made for individual rotational lines of the atmospheric oxygen $\text{b}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(ν′ = 2) ← X}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}\text{(ν″ = 0)}$ γ band by using a recently developed, highly sensitive, intracavity laser-absorption spectroscopic technique (ICLAS) at 300 torr m. The total band intensity derived from the line intensities is $\text{1.26 ± 0.05}\text{cm}{}^{\mathrm{?1}}\text{km}{}^{\mathrm{?1}}\text{atm}{}^{\mathrm{?1}}$ (STP). Self-broadening collision coefficients for the ^PP and ^PQ branch lines have been determined from the absorption line width and were found to vary from 0.055 cm^?1 atm^?1 at N″ = 1 to 0.037 cm^?1 atm^?1 at N″ = 27.     

Strengths and lorentz broadening coefficients for spectral lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4

Line strengths and self- and nitrogen-broadened half-widths were measured for spectral lines in the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ and ¹³CH₄ from 2870–2883 cm^?1 using a tunable diode laser spectrometer. From measurements made over a temperature range from 215 to 297 K, on samples of ¹²CH₄ broadened with N₂, we deduced that the average temperature coefficients n, defined as $\text{b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T) = b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T}{}_0\text{)(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{?n}}$, of the Lorentz broadening coefficients for the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ were 0.97 ± 0.03 and 0.89 ± 0.04, respectively. A smaller increase is observed in line half-width with increasing pressure for E-species lines, for both self- and nitrogen-broadening, than for other symmetry species lines over the range of pressures measured, 70 to 100 Torr.     

A study of the K = 3nA1 - A2 centrifugal splitting in the 3ν2 and 4ν2 states of PH3 using a difference-frequency laser system

A frequency tunable infrared source has been constructed by using the (Ar-laser) - (dyelaser) difference frequency method developed by Pine and applied to the observation of the overtone bands of PH₃ 3ν₂ ← 0 and 4ν₂ ← ν₂ in the 3.4 μm region and 4ν₂ ← 0 in the 1.6-μm region. A Stark modulation method was used to increase the sensitivity of detection. For transitions which were well modulated, the minimum detectable absorption coefficient was estimated to be ～3 × 10^?7 cm^?1 using a 3-m cell. Emphasis was placed on the observation of the A₁-A₂ splitting for K = 3n rotational levels. For the 3ν₂ state splittings were observed for K = 3, 6, and 9 because PH₃ is a very nearly spherical top in this state. The magnitude and the J dependence of the observed K = 3n splittings have been analyzed by using a normal symmetric rotor Hamiltonian and a centrifugal distortion term of the form $\text{τ}{}_{\mathrm{xxxz}}\text{[(J}{}_{\mathrm{+}}{}^3\text{+ J}{}_{\mathrm{?}}{}^3\text{)J}{}_{\mathrm{z}}\text{+ J}{}_{\mathrm{z}}\text{(J}{}_{\mathrm{+}}{}^3\text{+ J}{}_{\mathrm{?}}{}^3\text{)]}\text{4}$.     

Electric field-induced spectrum of carbon disulfide: Excited state dipole moment

The electric field-induced spectrum of carbon disulfide vapor has been observed in a number of vibronic bands in the 3300–3750 Å region of the $\text{B}{}_2\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ electronic system. A detailed analysis of the Σ0^g+2 band at 29 241.8 cm^?1 has yielded the electric dipole moment of the bent excited state of the transition as 0.7 ± 0.1 D.Consideration of the lineshapes of the EFS lines in this band gives a confirmation of the value of A′ near 4.3 cm^?1. The ratio of induced absorption intensities perpendicular and parallel to the applied field in various bands correlates with the band-type assignments of Klemens.     

Spectrum and structure of the He2 molecule: Characterization of the triplet states associated with (1σg)2(1σu)nsσ, ndσ, ndπ, and ndδ (n = 5–12)

Emission spectra for the electronic transitions $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 2pπ b}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 5–12)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 2pπ b}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 5–12)}$, $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 3pσ c}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 5–10)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 3pσ c}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 5–11)}$, $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 3pπ e}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 6–11)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 3pπ e}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 6–11)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 4pσ g}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 9–11)}$, and $\text{10dδ}{}^3\text{Δ}{}_{\mathrm{u}}\text{→ 4pσ g}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ of ⁴He₂ are reported and the electronic structure of the triplet states associated with v = 0 of (1σ_g)²(1σ_u) nsσ and ndλ characterized. The energy levels comprising the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ and the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)ndλ(}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{)}$ manifolds exhibit strong channel mixing, while the mixing of the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ with the $\text{nd(}{}^3\text{λ}\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ channel structure is relatively minor. Models based on multichannel quantum defect theory are used to aid in the spectral assignments and to correlate the observed level structures. We show that three-limit and two-limit models adequately represent the bulk of the observed $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ and $\text{ndλ(}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{)}$ channel structures, respectively.     

The electronic isotope shift in the A2Π-X2Σ+ bands of BeH,BeD and BeT

The 0-0, 1-1, 2-2, and 3-3 bands of the A²Π-X²Σ⁺ transition of the tritiated beryllium monohydride molecule have been observed at 5000 Å in emission using a beryllium hollow-cathode discharge in a He + T₂ mixture. The rotational analysis of these bands yields the following principal molecular constants.

$\text{A}{}^2\text{Π:}\text{B}{}_{\mathrm{e}}\text{= 4.192}\text{cm}{}^{\mathrm{?1}}\text{; r}{}_{\mathrm{e}}\text{= 1.333}\text{A}\text{?}$

$\text{X}{}^2\text{Σ:}\text{B}{}_{\mathrm{e}}\text{= 4.142}\text{cm}{}^{\mathrm{?1}}\text{; r}{}_{\mathrm{e}}\text{= 1.341}\text{A}\text{?}$

$\text{ω}{}_{\mathrm{e}}\text{′ ? ω}{}_{\mathrm{e}}\text{″ = 16.36}\text{cm}{}^{\mathrm{?1}}\text{; ω}{}_{\mathrm{e}}\text{′X}{}_{\mathrm{e}}\text{′ ? ω}{}_{\mathrm{e}}\text{″X}{}_{\mathrm{e}}\text{″ = 0.84}\text{cm}{}^{\mathrm{?1}}$

From the pure electronic energy difference (E_Π - E_Σ)_BeT = 20 037.91 ± 1.5 cm^?1 and the corresponding previously known values for BeH and BeD, the following electronic isotope shifts are derived

$\text{ΔE}{}_{\mathrm{e}}{}^{\mathrm{i}}\text{(}\text{BeH}\text{?}\text{BeT}\text{) = ?4.7 ≠ 1.5}\text{cm}{}^1\text{, ΔE}{}_{\mathrm{e}}{}^{\mathrm{i}}\text{(}\text{BeH}\text{?}\text{BeT}\text{) = ?1.8 ≠ 1.5}\text{cm}{}^1$

and related to the theoretical approach given by Bunker to the problem of the breakdown of the Born-Oppenheimer approximation.     

The emission spectrum of B2

The emission spectrum of B₂ was reinvestigated under high resolution. Six bands of ¹¹B₂ (0-0, 1-1, 1-0, 2-1, 3-2, and 0–1) as well as four bands of ¹⁰B¹¹B (0-0, 1-0, 2-1, and 3-2) were rotationally analysed. Accurate rotational and vibrational constants were obtained. The triplet character of the transition (${}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{-X}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$) was unambiguously established for the first time and spin-spin interaction constant is obtained for the excited state.     

Ultraviolet absorption spectra of Zn2 and Cd2 in solid argon and krypton at 10 K

Zinc and cadmium atoms have been condensed with argon and krypton at 10 K. The most intense absorption is due to the ${}^1\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic transition, and a weak band is due to the ${}^3\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic absorption. Structured absorptions at 252 and 254 nm in solid argon and krypton with vibrational spacings of 140-120 cm^?1 are due to the ${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transition of Zn₂. Similar 273 and 277 nm absorptions with 110-90 cm^?1 vibrational spacings are due to Cd₂ in solid argon and krypton, respectively.