Rotational analysis of the B3Π(0+) → X1Σ+ band systems of 35Cl35Cl and 35Cl37Cl in the chlorine afterglow emission spectrum

The B³Π(0⁺) → X¹Σ⁺ band system of Cl₂, excited by the recombination of ground state $\text{Cl}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ atoms at total pressures near 2 Torr, has been rotationally analyzed in the range 6300–9900 Å. About 30 bands, with 0 ≤ v′ ≤ 6 and 5 ≤ v″ ≤ 14, were investigated, mostly for both ³⁵Cl³⁵Cl and ³⁵Cl³⁷Cl. The band origins and rotational constants for the B state were obtained with the help of the known constants for the ground state. The principal molecular constants (cm^?1) for the B³Π(0⁺) state of ³⁵Cl³⁵Cl are as follows: T_e′ = 17 817.67(3); ω_e′ = 255.38(3); ω_e′x_e′ = 4.59(1); ω_e′y_e′ = ?0.038(8); D_e′ = 3341.17(14); B_e′ = 0.16313(3); α_e′ = 2.42(3) × 10^?3; γ_e′ = ?5.7(7) × 10^?5. The equilibrium internuclear separation is 2.4311(2) Å. The results of Briggs and Norrish on a transient absorption spectrum of Cl₂ assigned as $\text{0}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{← B}{}^3\text{Π}\text{(0}{}^{\mathrm{+}}\text{)}$ are reinterpreted with the present constants.     

A spectrum of rhenium oxide

The arc emission spectrum of the ReO molecule has been photographed in the region 590–860 nm and three bands of a single electronic transition have been rotationally analyzed. The separation of lines of the isotopic molecules ¹⁸⁵ReO and ¹⁸⁷ReO leads to the conclusion that the vibrational assignments for these bands are 1-0, 0-0, and 0–1. It is conceivable that an electronic isotope shift of ～0.08 cm^?1 exists. The following vibrational and rotational data (cm^?1) have been determined: ν₀(0-0) = 14 038.42, $\text{Δ}\text{G′(}\text{1}\text{2}\text{) = 867.85}$, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.14}$; B′_e = 0.3889, α′_e = 0.0019, B″_e = 0.4257, α″_e = 0.0043. It is concluded that Λ′ ? Λ″ = +1 with Λ″ ≥ 2.     

The D′ → A′ transition in Br2

A vibrational and rotational analysis is presented for the D′ → A′ transition (2800–2950 Å) of Br₂. The analysis includes 11 rotationally analyzed bands for ⁷⁹Br₂ and 3 for ⁸¹Br₂, plus bandheads for 70 additional v′-v″ bands of ⁷⁹Br₂, ⁸¹Br₂, and ⁷⁹Br⁸¹Br. The latter include some violet-degraded and spikelike features at the long-wavelength end of the spectrum, which are interpreted and assigned with the aid of band profile simulations. The assigned features are fitted directly to 14 vibrational and rotational expansion parameters for the two electronic states, from which the following spectroscopic constants are obtained: ΔT_e = 35706 cm^?1, ω′_e = 150.86 cm^?1, ω″_e = 165.2 cm^?1, B′_e = 0.042515 cm^?1, B″_e = 0.05944 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.170}\text{A}\text{?}$, $\text{R″}{}_{\mathrm{e}}\text{= 2.681}\text{A}\text{?}$. The spectroscopic parameters are used to calculate RKR potentials and Franck-Condon factors for the transition.     

The visible and photographic infrared spectrum of osmium oxide

The emission spectrum of OsO has been photographed in the region 405–875 nm where many new bands have been observed. In favorable cases the ${}^{190}\text{OsO}{}^{192}\text{OsO}$ isotopic splittings have been resolved and aid in vibrational assignments. Three visible bands in the region 433–470 nm have been assigned as (1,0), (0,0), and (0,1) of a $\text{ΔΩ}\text{= 0}$ electronic transition. The (0,0) and (0,1) bands have been rotationally analyzed, yielding principal constants (cm^?1) for the visible system of ν₀ = 22 273.3, B′₀ = 0.3657, D′₀ = 2.8 × 10^?7, B″_e = 0.4023, D″_e = 3.2 × 10^?7, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 780.7}$, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 884.9}$. A band at 825.4 nm has been found to be a $\text{ΔΩ}\text{= +1}$ (0,0) band with the same lower state as in the analyzed visible bands. Constants for the upper state of the ir system are ν₀ = 12 109.7, B′₀ = 0.3845, and D′₀ = 3.1 × 10^?7 cm^?1.     

Microwave optical double resonance and continuous wave dye laser excitation spectroscopy of NO2: Rotational assignment of the K = 0−4 subbands of the 593 nm band

A rotational assignment of approximately 80 lines with K_a′ = 0, 1, 2, 3, and 4 has been made of the 593 nm ${}^2\text{A}{}_1\text{→}{}^2\text{B}{}_2$ band of NO₂ using cw dye laser excitation and microwave optical double-resonance spectroscopy. Rotational constants for the ²B₂ state were obtained as A = 8.52 cm^?1, B = 0.458 cm^?1, and C = 0.388 cm^?1. Spin splittings for the K_a′ = 0 excited state levels fit a simple symmetric top formula and give $\text{(?}{}_{\mathrm{bb}}\text{+ ?}{}_{\mathrm{cc}}\text{)}\text{2}\text{= ?0.0483}\text{cm}{}^{\mathrm{?1}}$. Spin splittings for K_a′ = 1 (N′ even) are irregular and are shown to change sign between N′ = 6 and 8. Assuming that the large inertial defect of 4.66 amu Ų arises solely from A, a structure for the ²B₂ state is obtained which gives $\text{r}\text{(NO) = 1.35}\text{A}\text{?}$ and an ONO angle of 105°. Alternatively, weighting the three rotational constants equally gives $\text{r = 1.29}\text{A}\text{?}$ and θ = 118°.     

Determination of molecular constants of nitric oxide from (1-0), (2-0), (3-0) bands of the 15N16O and 15N18O isotopic species

The (1-0), (2-0), and (3-0) transitions of ¹⁵N¹⁶O and ¹⁵N¹⁸O are investigated. The wavenumbers of the rotation-vibration lines are reported for the overtone bands and the ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ (1-0) subband. It is shown that in the data reduction it is advantageous to calculate first merged spectroscopic constants ignoring the Λ-type doubling. The vibrational constants ω_e, ω_ex_e, ω_ey_e and the vibrational dependence of the rotational constants are determined. The study of ¹⁵N¹⁸O allows the determination of the equilibrium values of the centrifugal distortion correction A_De to the spin-orbit constant and of the spin-rotation constant γ_e from the isotopic invariance of the ratios $\text{A}{}_{\mathrm{<mtext>De</mtext>}}\text{B}{}_{\mathrm{<mtext>e</mtext>}}$ and $\text{γ}{}_{\mathrm{<mtext>e</mtext>}}\text{B}{}_{\mathrm{<mtext>e</mtext>}}$. It is found that $\text{A}{}_{\mathrm{<mtext>De</mtext>}}\text{B}{}_{\mathrm{<mtext>e</mtext>}}\text{= (?3.9 ± 1.3) × 10}{}^{\mathrm{?6}}$ and $\text{γ}{}_{\mathrm{<mtext>e</mtext>}}\text{B}{}_{\mathrm{<mtext>e</mtext>}}\text{= (?4.00 ± 0.05) × 10}{}^{\mathrm{?3}}$.     

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.     

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, $\text{R′}{}_{\mathrm{e}}\text{= 3.53}\text{A}\text{?}$.     

Fourier spectrometry: Rovibrational analysis of an infrared 1Π → 1Σ system of yttrium monoiodide

The infrared spectrum of yttrium monoiodide has been excited in an electrodeless microwave discharge and explored between 2500 and 12 000cm^?1 with a high-resolution Fourier transform spectrometer. A unique system is observed (ν₀₀ = 9905.520 cm^?1), which we attribute to a ${}^1\text{Π}\text{→}{}^1\text{Σ}$ transition and an extensive analysis is made. Rovibrational constants are obtained for both states mainly from a simultaneous multiband fitting. This procedure is applied to the whole set of 2231 observed line wavenumbers in the 1-0, 0-0, and 0–1 bands, yielding a final weighted standard deviation of 0.0038 cm^?1. Furthermore, a partial analysis of the 2-0 and 3-1 bands is performed. The following equilibrium constants are derived (cm^?1):

$\text{ω′}{}_{\mathrm{e}}\text{=192.210 ω′}{}_{\mathrm{e}}\text{x′}{}_{\mathrm{e}}\text{=0.463}$

$\text{B′}{}_{\mathrm{e}}\text{=0.0399133 α′}{}_{\mathrm{e}}\text{=0.0001150}$

$\text{ω″}{}_{\mathrm{e}}\text{=215.815 ω″}{}_{\mathrm{e}}\text{x″}{}_{\mathrm{e}}\text{=0.514}$

$\text{B″}{}_{\mathrm{e}}\text{=0.0422163 α″}{}_{\mathrm{e}}\text{=0.0001125}$

High-order constants D_v and H_v are also calculated for the various vibrational levels (v′ = 0, 1, 2, 3; v″ = 0, 1).     

The A′(3Π2) state of ICl

Although $\text{A′(}{}^3\text{Π}{}_2\text{) ← X(}{}^1\text{Σ}{}^{\mathrm{+}}\text{)}$ is forbidden in near case c molecules the A′ ← X transition can be efficiently accomplished by the three-step sequence $\text{A′(}{}^3\text{Π}{}_2\text{) ← D′(2) ← A(}{}^3\text{Π}{}_1\text{) ← X(}{}^1\text{Σ}{}^{\mathrm{+}}\text{)}$. Transitions to a range of levels of A′, v_A′ = 2–38, have been recorded by this means, using J-selective polarization-labeling spectroscopy. Principal constants of the A′ state of I³⁵Cl are T_e = 12682.05, ω_e = 224.57, ω_eχ_e = 1.882, ω_ey_e = ?0.0107, B_e = 0.08653, and α_e = 0.000675 cm^?1. The A′ state is therefore similar in its physical characteristics to two other (relatively) deep states, $\text{A(}{}^3\text{Π}{}_1\text{)}$ and $\text{B(}{}^3\text{Π}{}_0\text{+)}$, of the 2431 configuration.     

The D′ → A′ transition in I2

A detailed vibrational analysis is given for the D′(2g) → A′(2u³Π) transition (3300–3460 Å) in I₂. The assignments include ～ 150 v′-v″ bands in ¹²⁷I₂ and ～100 in ¹²⁹I₂, spanning v′ levels 0–15 and v″ levels 4–30. These bands are mainly red-degraded but include some violet-degraded and line-like features. The analysis is corroborated by Franck-Condon and band profile calculations. The least-squares fit yields the following constants (cm^?1); ΔT_c = 30 340.8, ω′_e = 103.95, ω_eχ′_e = 0.206, ω″_e = 106.1, ω_eχ″_e = 0.81. Anomalous behavior in the vibrational level structure above v″ = 23 makes the extrapolation to the A′ dissociation limit uncertain, so the absolute energies of both states remain ill-defined. However there is a possibility that the D′ state is the state labeled α by King et al. [Chem. Phys. 56, 145–156 (1981)], in which case the energies are known precisely. There is evidence of weak emission from at least two other electronic transitions in this spectral region, probably $\text{D(0}{}^{\mathrm{+}}\text{u) → X(}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{)}$ ($\text{λ}\text{< 3300}\text{A}\text{?}$) and β → A(1u³Π) ($\text{λ}\text{> 3300}\text{A}\text{?}$).     

Spectroscopic information on ground-state Ar2, Kr2, and Xe2 from interatomic potentials

Calculations of vibrational and rotational level spacings of homonuclear inert gas diatomic molecules by numerical integration of the radial Schrödinger equation are presented. The potentials which were used for the ground states of Ar₂, Kr₂, and Xe₂ were obtained from accurate fits to the molecular beam scattering data. From the calculated $\text{Δ}\text{G}{}_{\mathrm{<mtext>v+</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{'}\text{s}$ and B_v's, the following spectroscopic constants (in cm^?1) were fitted: for Ar₂ω_e = 31.92, ω_ex_e = 3.31, ω_ey_e = 0.11, B_e = 0.060, α_e = 0.004; for $\text{Kr}{}_2\text{ω}{}_{\mathrm{e}}\text{? 23.99}$, $\text{ω}{}_{\mathrm{e}}\text{x}{}_{\mathrm{e}}\text{? 1.30}$, $\text{ω}{}_{\mathrm{e}}\text{y}{}_{\mathrm{e}}\text{? 0.021}$, $\text{B}{}_{\mathrm{e}}\text{? 0.024}$, $\text{α}{}_{\mathrm{e}}\text{? 0.001}$; for $\text{Xe}{}_2\text{ω}{}_{\mathrm{e}}\text{? 21.26}$, $\text{ω}{}_{\mathrm{e}}\text{x}{}_{\mathrm{e}}\text{? 0.75}$, $\text{ω}{}_{\mathrm{e}}\text{y}{}_{\mathrm{e}}\text{? 0.008}$, $\text{B}{}_{\mathrm{e}}\text{? 0.013}$, $\text{α}{}_{\mathrm{e}}\text{? 0.0004}$.     

A new electronic band system of PbO

The chemiluminescence spectrum of atomic Pb reacting with O₃ under single-collision conditions includes a series of 55 bands in the regions 450–850 nm. A vibrational analysis is obtained which shows emission is to the ground state of PbO from excited electronic states not previously analyzed. Forty-nine of the bands are assigned to the a(1)-X(0⁺) transition and the remaining six are tentatively identified as the forbidden b(0^?)-X(0⁺) transition. Both the a and b states are believed to be Hund's case (c) components of the ³Σ⁺ states arising from the configuration $\text{σ}{}^2\text{π}{}^3\text{π}{}^1$. The vibrational parameters of the a state are ν₄ = 16 029 ± 8, ω_e′ = 478.7 ± 1.9, and ω_ex_e′ = 2.292 ± 0.128 cm^?1, where the uncertainties represent two standard deviations of the least-squares fit. Emission is also observed from the PbO B state produced in the reaction of metastable Pb atoms with O₃. Using pulsed laser excitation, an attempt is made to determine radiative lifetimes. We find for the PbO A(0⁺) state τ = 3.74 ± 0.3 μsec, and for the PbO B(1) state τ = 2.58 ± 0.3 μsec, while for the a(1) state τ is estimated to be greater than 10 μsec. From the vibrational analysis, energy conservation arguments place a lower limits to the ground state dissociation energy of $\text{D}{}_0{}^0\text{(}\text{PbO}\text{) ≥ 3.74 ± 0.03}\text{eV}$ (86.2 ± 0.7 kcal/mole). For the Pb + O₃ reaction we find less than 1% of the products are PbO¹ molecules that emit in the visible. Correlations are made with the low-lying states of other Group IV chalconides based on the assignment of the PbO $\text{a}{}^3\text{Σ}{}^{\mathrm{+}}\text{(1)}$ state and the correspondence between the low-lying triplet states of PbO and CO.     

Overtone bands of 14N16O and determination of molecular constants

The wavenumbers of the rotation-vibration lines of ¹⁴N¹⁶O are reported for the (2-0) and (3-0) bands. The full set of spectroscopic constants for the three bands (1-0), (2-0), and (3-0) has been determined with the method developed by Albritton, Schmeltekopf, and Zare for merging the results of separate least-squares fits. The vibrational constants ω_e, ω_ex_e, ω_ey_e, and the vibrational dependence of the rotational constants have been deduced. The apparent spin-orbit constant $\text{A}\text{?}{}_{\mathrm{<mtext>v</mtext>}}$ and its centrifugal correction $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext>}}$ (including the spin-rotation constant) have a vibrational dependence of the following form: $\text{A}\text{?}{}_{\mathrm{v}}\text{=}\text{A}\text{?}{}_{\mathrm{e}}\text{? α}{}_{\mathrm{A}}\text{(v +}\text{1}\text{2}\text{) + γ}{}_{\mathrm{A}}\text{(v +}\text{1}\text{2}\text{)}{}^2$ and $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>v</mtext>}}\text{=}\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>e</mtext>}}\text{? β}{}_{\mathrm{A}}\text{(v +}\text{1}\text{2}\text{) + δ}{}_{\mathrm{A}}\text{(v +}\text{built+1}\text{2}\text{)}{}^2$; the values of the constants in these two equations have been determined.     

Sequential two-photon spectroscopy of some ion-pair states of IBr

Molecular constants of the first E 0⁺ ion-pair state of IBr vapor have been determined using polarization-labeling spectroscopy applied to the sequential transitions E 0⁺ ← B′ 0⁺ ← X 0⁺, while the second f 0⁺ ion-pair state is reported and characterized for the first time. A least-squares, simultaneous analysis of data for the I⁷⁹Br and I⁸¹Br isotopes gives the following constants (in cm^?1) for I⁷⁹Br:

$\text{E}\text{state}\text{: T}{}_{\mathrm{<mtext>e</mtext>}}\text{= 39487.32(12), ω}{}_{\mathrm{<mtext>e</mtext>}}\text{= 119.518(21), ω}{}_{\mathrm{<mtext>e</mtext>}}\text{ξ}{}_{\mathrm{<mtext>e</mtext>}}\text{= 0.2109(12)}$

,

$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{y}{}_{\mathrm{<mtext>e</mtext>}}\text{= ? 2.34(22) × 10}{}^{\mathrm{?4}}\text{, B}{}_{\mathrm{<mtext>e</mtext>}}\text{= 2.9701(14) × 10}{}^{\mathrm{?2}}$

,

$\text{α}{}_{\mathrm{<mtext>e</mtext>}}\text{= 5.43(59) × 10}{}^{\mathrm{?5}}\text{,}\text{and}\text{γ}{}_{\mathrm{<mtext>e</mtext>}}\text{= ? 6.8(16) × 10}{}^{\mathrm{?7}}$

.

$\text{F}\text{state}\text{: T}{}_{\mathrm{<mtext>e</mtext>}}\text{= 45382.58(17), ω}{}_{\mathrm{<mtext>e</mtext>}}\text{= 128.805(66), ω}{}_{\mathrm{<mtext>e</mtext>}}\text{ξ}{}_{\mathrm{<mtext>e</mtext>}}\text{= 0.3630(69)}$

,

$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{y}{}_{\mathrm{<mtext>e</mtext>}}\text{= ? 9.7(22) × 10}{}^{\mathrm{?4}}\text{, B}{}_{\mathrm{<mtext>e</mtext>}}\text{= 3.0073(30) × 10}{}^{\mathrm{?2}}\text{,}\text{and}\text{α}{}_{\mathrm{<mtext>e</mtext>}}\text{= 8.52(48) × 10}{}^{\mathrm{?5}}$

. Preliminary data for the first $\text{Ω}\text{= 1}$ ion-pair state, accessed in the sequence $\text{1(}{}^3\text{P}{}_2\text{) ← A(}\text{Ω}\text{= 1) ← X 0}{}^{\mathrm{+}}$, indicate that T_e is ?30 cm^?1 higher in energy than that of the E state.     

Rotational analyses and vibrational assignments of the 463- and 474-nm bands of NO2

The excitation spectrum of NO₂ was investigated in the blue region by using a Nd:YAG laser-pumped dye laser. The 463- and 474-nm bands of the ²B₂-²A₁ system were identified and analyzed using the simplification that occurs if the excitation spectrum is monitored at particular wavelengths. Band origins and rotational constants were obtained. Vibrational assignments have been given to these bands by comparing the Franck-Condon Factors calculated for the ²B₂-²A₁ system with the fluorescence intensities of bands going to different vibrational levels of the ground state. The vibrational assignments and molecular constants obtained in this work are (v′₁, v′₂, v′₃) = (3, 11, 0)ν₀(K′ = 0) = 21584.1, $\text{B}\text{= 0.405}$, and $\text{∥}\text{?}\text{′∥ = 0.05}\text{cm}{}^{\mathrm{?1}}$ for the 463-nm band; and (v′₁, v′₂, v′₃) = (2, 12, 0), ν₀(K′ = 1) = 21104.9, $\text{B}\text{= 0.408}$, and $\text{∥}\text{?}\text{′∥ = 0.03}\text{cm}{}^{\mathrm{?1}}$ for the 474-nm band.     

Two emission systems of BS

Two new systems of emission bands near 2100 and 3100 Å have been produced by a microwave discharge in B₂S₃ vapor. From the known X²Σ⁺ and A²Π_i states of BS, these systems have been assigned as E²Σ⁺ → X²Σ⁺ and E²Σ⁺ → A²Π_i. Constants in cm^?1 for the new state are

$\text{E}{}^2\text{∑}{}^{\mathrm{\pm }}\text{: T}{}_{\mathrm{e}}\text{= 47 929.3, B}{}_{\mathrm{e}}\text{= 0.671 (λ}{}_{\mathrm{e}}\text{= 1.752 A), α}{}_{\mathrm{e}}\text{= 0.008}$

,     

High resolution Fourier spectroscopy of P2 infrared emission spectrum: Analysis of two new systems b3Πg → w3Δu and A1Πg → W1Δu

The investigation of the emission infrared spectrum of P₂ was performed with a high resolution Fourier spectrometer. Two new electronic systems were attributed to b³Π_g → w³Δ_u and A¹Π_g → W¹Δ_u transitions. The molecular parameters are obtained by a complete fitting procedure. The main equilibrium constants of the new states are (in cm^?1):

$\text{ω}{}^3\text{Δ}{}_{\mathrm{u}}\text{T}{}_{\mathrm{e}}\text{= 243228.07 ω}{}_{\mathrm{e}}\text{= 591.3 ω}{}_{\mathrm{e}}\text{X}{}_{\mathrm{e}}\text{= 2.5}$

$\text{B}{}_{\mathrm{e}}\text{= 0.256040 δ}{}_{\mathrm{e}}\text{= 0.001409 D}{}_{\mathrm{e}}\text{= 19.0 X 10}{}^{\mathrm{?8}}$

$\text{W}{}^1\text{Δ}{}_{\mathrm{u}}\text{T}{}_{\mathrm{e}}\text{= 31096.64 W}{}_{\mathrm{e}}\text{= 627.206 W}{}_{\mathrm{e}}\text{X}{}_{\mathrm{e}}\text{= 2.331}$

$\text{B}{}_{\mathrm{e}}\text{= 0.2628 δ}{}_{\mathrm{e}}\text{= 0.0014 D}{}_{\mathrm{e}}\text{= 23 X 10}{}^{\mathrm{?8}}$

     

Rotational constants of the E O+g state of I2 determined by polarization spectroscopy

The resonant 2-photon E(O⁺_g) ← B(O⁺_g) ← X(O⁺_g) transition of I₂ vapor has been studied by polarization spectroscopy, leading to a rotational analysis of the ν = 0–15 vibrational levels of the E state. The principal constants determined are $\text{B}{}_{\mathrm{e}}\text{= 19.9738(42) × 10}{}^{-3}\text{, α}{}_{\mathrm{e}}\text{= 5.602(84) × 10}{}^{-5}\text{, γ}{}_{\mathrm{e}}\text{= 1.02(41) × 10}{}^{-7}\text{, D}{}^{\mathrm{e}}{}_{\mathrm{J}}\text{= 3.040(74) × 10}{}^{-9}\text{cm}{}^{-1}\text{, and r}{}_{\mathrm{e}}\text{= 3.6470(5)}\text{A}\text{?}$.     

The Ã1B2-X̃1A1 two-photon fluorescence excitation spectrum of 1,3-difluorobenzene

The $\text{A}\text{?}{}^1\text{B}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ system of 1,3-difluorobenzene has been observed using the technique of two-photon fluorescence excitation obtained with a pulsed dye laser. Calibration was achieved by a combination of the neon optogalvanic spectrum and etalon fringes. In circular, compared to linear, polarization the bands divide into two groups, those which are B₂-A₁ and which retain their intensity with circular polarization, and those which are A₁-A₁ and lose about 60% of their intensity under the same conditions. These two kinds of bands also show characteristic rotational contours. All of the A₁-A₁ bands whose assignments are established obtain their intensity through vibronic interaction in which the vibration ν′₂₅ (ν′₁₄ in the Wilson numbering) mixes the $\text{A}\text{?}$ with, presumably, the $\text{X}\text{?}$ state. There is an important Fermi resonance between the 9¹ and 10¹11¹ levels. Parts of the one-photon absorption spectrum have been photographed to identify sequences associated with the 0₀⁰ band for comparison with those observed in the two-photon spectrum, and to search for bands involving odd quanta of b₂ vibrations, including ν′₂₅ (ν′₁₄); none was found.