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:

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

;

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

.     

Rotation-vibration analysis of the Coriolis-coupled ν5g, ν6g, ν8g and ν9 bands of H2CCO

Medium resolution infrared grating spectra of gaseous ketene, H₂CCO were recorded between 1000 and 400 cm^?1, both at instrument temperature (40°C) and with cooling (?40°C). Interferometric Fourier spectra were also measured at ?70°C with resolution 0.22 cm^?1 between 450 and 330 cm^?1. The K structure of the fundamentals ν₅, ν₆, ν₈, and ν₉ was assigned. These fundamentals are coupled by a-axis Coriolis interactions. These couplings were analysed on the symmetric top basis for setting up the perturbation matrix and by utilizing the K-dependent Coriolis shifts of levels. A preliminary analysis of the Coriolis intensity anomalies was also undertaken.Band center values from combination differences are $\text{ν}{}_5{}^0\text{= 587.30 (27)}$ and $\text{ν}{}_6{}^0\text{= 528.36 (39)}\text{cm}{}^{\mathrm{?1}}$. Synthetic spectra indicate the band origins of ν₈ and ν₉ to be close to 977.8 and 439.0 cm^?1, respectively. Estimates of Coriolis coupling constants obtained from synthetic spectra are $\text{ζ}{}_{58}{}^{\mathrm{a}}\text{= + 0.33 (5)}$, $\text{ζ}{}_{68}{}^{\mathrm{a}}\text{= + 0.714 (20)}$, $\text{ζ}{}_{59}{}^{\mathrm{a}}\text{= ? 0.774 (20)}$, and $\text{ζ}{}_{69}{}^{\mathrm{a}}\text{= ? 0.30 (2)}$. Approximate ratios of unperturbed vibrational transition moments obtained from spectral simulations are $\text{M}{}_8{}^0\text{:±iM}{}_5{}^0\text{:±iM}{}_6{}^0\text{:M}{}_9{}^0\text{≈ +2:?9:+10:+0.5}$.     

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.     

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.     

Laser-excited phosphorescence spectrum of C3S2 in an Ar matrix

The phosphorescence spectrum of C₃S₂ was observed in a low-temperature Ar matrix with excitation of an Ar⁺ laser. The spectrum consists of a very strong 0-0 band at 18 287 cm^?1 and well-resolved progressions in the ν₂, ν₅, ν₆, and ν₇ vibrations. Side bands were found on the high-energy sides of some transitions. The separation between the main and side bands is 23 cm^?1. Polarization analysis suggests that C₃S₂ is linear symmetric in the Phosphorescent state as in the ground electronic state. On the basis of symmetry considerations and a qualitative evaluation of spin-orbit coupling, the phosphorescent state is assigned to ³Σ_u^? with Σ_u⁺ and Π_u components split by spin-spin interaction. The Σ_u⁺ level is lower than the Π_u one by 23 cm^?1 and the main and side band emissions start from the Σ_u⁺ and Π_u levels, respectively. The Σ_u⁺ component seems to acquire allowed character from a ¹Σ_u⁺ state by spin-orbit coupling and from bent ${}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}\text{(}{}^1\text{B}{}_2\text{)}$ and ${}^1\text{Δ}{}_{\mathrm{g}}\text{(}{}^1\text{A}{}_1\text{+}{}^1\text{B}{}_2\text{)}$ states by ν₅ vibronic coupling. Mixing of the Σ_u⁺ and Π_u components through ν₅ is responsible for most of the side bands. The ν₅ frequency is estimated to be 160 ± 20 cm^?1 in the ³Σ_u^? state from the intensities of ν₅ progression bands and from the ground-state frequency, 411 cm^?1.     

Infrared diode laser spectroscopy of the CF radical

The fundamental bands of the CF radical in the $\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ electronic states were observed by using an infrared tunable diode laser as a source. Zeeman modulation could be used in detecting lines not only in the ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ state, but also in ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, because the CF radical deviates considerably from Hund's case (a). From the least-squares analysis of the observed spectra, the following molecular constants were obtained: B_e = 1.416 704 (37) cm^?1, α_e = 0.018 419 (50) cm^?1, $\text{r}{}_{\mathrm{e}}\text{= 1.271 977 (17)}\text{A}\text{?}$, D_e = 6.68 (15) × 10^?6cm^?1, p₀ = 0.008 580 (21) cm^?1, p₁ = 0.008 52 (11) cm^?1, and $\text{ν}{}_0\text{= 1286.1281 (5)}\text{cm}{}^{\mathrm{?1}}$, with three standard errors in parentheses.     

Vibration-rotation spectrum of formaldehyde: CH stretching fundamentals ν1 and ν5

The infrared vibration-rotation spectrum of formaldehyde vapor has been measured in the region from 2600 to 3400 cm^?1 with resolution from 0.04 to 0.07 cm^?1. An extensive rotational analysis of the ν₁ and ν₅ bands has confirmed and superseded the previous band-contour analysis of a medium-resolution spectrum. A large number of subbranches of both the ν₁ and ν₅ bands are perturbed by the combination bands ν₃ + ν₆, ν₂ + ν₄, and ν₂ + ν₆, whereas the Coriolis interaction between ν₁ and ν₅ is weak. The following effective rotational constants (in cm^?1) are obtained:

$\text{ν}{}_1\text{= 2782.49(1), A}{}_1\text{= 9.250(5), B}{}_1\text{= 1.2968(6), C}{}_1\text{= 1.1321(2)}$

,

$\text{ν}{}_0\text{= 2843.35(2), A}{}_0\text{= 9.224(2), B}{}_0\text{= 1.2936(2), C}{}_0\text{= 1.1303(1)}$

, where the number given in parentheses is three times the standard error in the last digit.     

Acetylene fluorescence

Previously unobserved acetylene ${}^1\text{A}{}_{\mathrm{u}}\text{(}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{) →}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ fluorescence occurs following 1933-Å ArF laser excitation of C₂H₂ or C₂H₄ and their deuterated analogs in solid Ne and Ar hosts at 4.2 K. Acetylene is a photolysis product of matrix-isolated ethylene. Ground-state vibrational levels as high as ν″₃ = 30 of the degenerate ν₃ bending vibration are observed for C₂D₂. Only ν₃ is appreciably active in the fluorescence. The negative ν₃ anharmonicity, previously observed in the gas phase, also occurs in Ne host. Consideration of rotational selection rules indicates that the Ne host strongly hinders free rotation about the low-moment-of-inertia $\text{a}\text{?}$ axis in the excited state.     

The laser magnetic resonance spectrum of the NCO radical at 5.2 μm

Lines in the ν₃ (“antisymmetric” stretch) fundamental of the NCO radical in the $\text{X}\text{?}{}^2\text{Π}$ state were studied by CO laser magnetic resonance. The observations were assigned to P and R lines in the vibration-rotation band and lead to a precise determination of the vibrational interval and the anharmonic correction to the rotational constant: ν₃ = 1920.60645(19) cm^?1, α₃ = 0.003338(21) cm^?1. A single transition in the hot band (011)-(010), ${}^2\text{Δ}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Δ}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ was detected. This observation is used to determine the origin of the hot band as 1907.11892(20) cm^?1, i.e., the anharmonicity parameter x₂₃ = ?13.48753(28) cm^?1.     

Analysis of the (ν1 + ν2) and (ν2 + ν3) combination bands of ozone

The fine structures of the (ν₁ + ν₂) and (ν₂ + ν₃) combination bands of ozone in the 5.7-μm region have been recorded and analyzed. The two vibrational states are coupled through Coriolis and second-order distortion terms. The interaction has been treated by the numerical diagonalization of the secular determinant for the two coupled states. With the centrifugal distortion parameters fixed to the ground state values, the following constants have been obtained: ν₁ + ν₂ = 1796.26₆, A₁₁₀ = 3.610₄, B₁₁₀ = 0.4414₅, $\text{C}{}^1{}_{110}\text{= 0.3902}{}_9$, ν₂ + ν₃ = 1726.52₆, A₀₁₁ = 3.553₇, B₀₁₁ = 0.4398₂, $\text{C}{}^1{}_{011}\text{= 0.3884}{}_4$, Y₁₃ = ?0.46₆, and X₁₃ = ?0.01₀ cm^?1. In addition, the following anharmonic constants have been obtained: x₁₂ = ?7.82₁ and x₂₃ = ?16.49₄ cm^?1. The value of the dipole moment ratio, $\text{R =}\text{〈011|μ}{}_{\mathrm{z}}\text{|0〉}\text{〈110|μ}{}_{\mathrm{x}}\text{|0〉}$, is 1.30 ± 0.10.     

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

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.     

Reorientational motion of the OH− ion in cubic sodium hydroxide

The rotational motion of the OH^? ion was studied in cubic NaOH at 575 K with quasielastic incoherent neutron scattering. The data are compared to two simple models yielding values for the radius of rotation R, the translational mean square displacement 〈u²〉_H, the rotational jump rate τ^?1 and the rotational diffusion coefficient D_R. The following parameter values are obtained: (a) rotational jump model: $\text{R = 0.95}\text{A}\text{?}$, $\text{〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.052}\text{A}\text{?}{}^2\text{, τ}{}^{\mathrm{?1}}\text{= 2}\text{meV}$, (b) rotational diffusion model: $\text{R = 0.99}\text{A}\text{?}\text{, 〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.046}\text{A}\text{?}{}^2\text{, D}{}_{\mathrm{R}}\text{= 0.72}\text{meV}$.     

The 2780 Å absorption system of thiophosgene

The vapor phase absorption spectrum of thiophosgene (Cl₂CS) in the 2500–2900 Å region consists of a broad intense band ($\text{log}\text{?}{}_{\mathrm{<mtext>max</mtext>}}\text{= 3.5}\text{at}\text{2540}\text{A}\text{?}$. On the red side of this a vibrationally discrete structure is found which becomes increasingly diffuse and merges into the broad band as the wavelength is decreased. It is shown that this vibrational structure can be explained as due to a $\text{π → π}{}^1$, ${}^1\text{A}{}_1\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ electronic transition between a planar ground state and a pyramidal excited state of the molecule. In the latter state, the CS stretching mode ν₁′(a₁) = 681 cm^?1 and the CCl bending mode ν₃′(a₁) = 147 cm^?1. From the inversion doublet splitting of the out-of-plane mode ν₄′(b₁), the barrier to inversion is calculated to be ～126 cm^?1, with an equilibrium out-of-plane angle of ～20°.     

Infrared spectrum of acetonitrile: Analysis of Coriolis resonance

The Coriolis resonance between ν₄ and ν₇ in CH₃CN and between ν₁ and ν₅, ν₃ and ν₆, and ν₄ and ν₇ in CD₃CN has been analyzed, applying the technique developed by DiLauro and Mills, to obtain the signs of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] and the ratio of $\text{?μ}\text{?Q}{}_{\mathrm{r}}$ to $\text{?μ}\text{?Q}{}_{\mathrm{s}}$ for the interacting pairs in CD₃CN. For (ν₄, ν₇) in both CH₃CN and CD₃CN, the sign of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] is found to be negative as it is also for (ν₁, ν₅) in CD₃CN. For (ν₃, ν₆) the sign of this interaction term is found to be positive. For a given definition of normal coordinates the signs of these interaction terms give the relative signs of $\text{?p}\text{?Q}{}_{\mathrm{r}}$ and $\text{?p}\text{?Q}{}_{\mathrm{sa}}$; our study also gives approximate values for the corresponding ratio [$\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)}\text{(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$]     

Infrared bands of 12C2HD

The rotational structure of about 40 bands of ¹²C₂HD observed in the region 6000?600 cm^?1 has been measured and interpreted with the purpose of determining a comprehensive set of molecular constants for this isotopic variety of acetylene. Combining these data with the results for ¹²C₂H₂ and ¹²C₂D₂, a reevaluation of the equilibrium internuclear distances for the acetylene molecule has been made: $\text{r}{}_{\mathrm{e}}\text{(CH) = 1.06215 ± 17 × 10}{}^{\mathrm{?5}}\text{A}\text{?}$ and $\text{r}{}_{\mathrm{e}}\text{(CC) = 1.20257 ± 9 × 10}{}^{\mathrm{?5}}\text{A}\text{?}$ were obtained. This paper presents all the molecular constants derived in this study.     

Diode laser measurements of strengths,half-widths,and temperature dependence of half-widths for CO2 spectral lines near 4.2 μm

Absolute line strengths have been measured at room temperature for spectral lines in the R branch of the ν₃ band of ¹²C¹⁶O₂, ¹²C¹⁶O¹⁸O, and ¹²C¹⁶O¹⁷O and the (ν₂ + ν₃) ? ν₂ and (ν₁ + ν₃) ? ν₁ bands of ¹²C¹⁶O₂ in the region 2365–2393 cm^?1 using a tunable diode laser spectrometer; from these measurements band strengths have been computed. Self- and nitrogen-broadened half-widths have been measured for some ν₃ lines of ¹²C¹⁶O₂ and ¹²C¹⁶O¹⁷O, and nitrogen-broadened half-widths measured for some (ν₂ + ν₃) ? ν₂ band lines of ¹²C¹⁶O₂. From measurements made over a temperature range from 217 to 299 K we have obtained temperature coefficients n, for the N₂-broadened Lorentz half-width defined as $\text{b}{}_{\mathrm{L}}{}^0\text{(T) = b}{}_{\mathrm{L}}{}^0\text{(T}{}_0\text{)(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{?n}}$, for the ν₃ and (ν₂ + ν₃) ? ν₂ bands of ¹²C¹⁶O₂. They are 0.757 ± 0.008 and 0.789 ± 0.015, respectively.     

Rotational analysis and radiative lifetime measurement on the 2B1 (K′ = 0) excited state of NO2 with v′2 = 6, 7, 8, and 9

The rotational structure of the ²B₁ (K′ = 0) subbands of NO₂ with v′₂ = 6, 7, 8, and 9 were analyzed by means of the time-gated excitation spectrum. The excitation spectrum monitored at ν₂, 2ν₂, or 3ν₂ fluorescence band was fairly simplified in comparison to its corresponding absorption spectrum. The band origins and rotational constants are evaluated from the observed data: ν₀ = 20205.0 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 6; ν₀ = 21104.4 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 7; ν₀ = 22001.9 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 8ν₀ = 22898.0 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 9. The value of $\text{B}\text{′}$ extrapolated to v′ = 0 is 0.370 cm^?1. This value corresponds to the bond length of 1.19 Å. Fluorescence decays of these excited levels were also studied. Radiative lifetimes obtained by extrapolation to zero pressure from the $\text{1}\text{τ}\text{– P}$ plots were 25–40 μsec. The short-lived excited levels previously reported by some authors were not found.     

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.     

Reexamination of the I2 spectrum near the B(3Π0u+) state dissociation limit

The disagreement of Danyluk and King's (Chem. Phys.25, 343 (1977)) rotational constants for levels lying near the dissociation limit of B-state I₂ with the mechanical behavior predicted by near-dissociation theory is investigated. The discrepancies are shown to be much too large to be explained by either the neglect of centrifugal distortion effects in the original analysis or by rotational or spin-rotation coupling to a nearby repulsive 1_u state. These differences are therefore attributed to experimental error, a conclusion which is confirmed by more recent experimental results. A reanalysis of the best available data for levels near the dissociation limit of B-state I₂ then yields improved values for the B-state dissociation limit $\text{D}$ = 20 043.16 (±0.02) cm^?1 of the vibrational index at dissociation v_$\text{D}$ = 87.32 (±0.04) and of the long-range potential constant $\text{C}{}_5\text{= 2.88 (±0.03) × 10}{}^5\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^5$. This in turn implies a slightly improved ground-state dissociation energy of $\text{D}$₀ = 12 440.18 (±0.02) cm^?1.