Intensity of the sulfur dioxide rotational spectrum

The integral band intensity of the pure rotational absorption of SO₂ gas has been determined from far-i.r. spectra. From the curve of growth, the value at 298°K is found to be S^o_b = 35.2±1.5atm^-1 -cm^-2. The entire set of experimental data has been analyzed using an absorption band model. The derived intensity agrees with that obtained from the curve of growth to be better than 10%. This result should be of value in connection with atmospheric models of the planet Venus.     

The sub-millimeter and Fourier transform microwave spectrum of HZnCl (X Σ)

The pure rotational spectrum of HZnCl (X ¹Σ⁺) has been recorded using sub-millimeter direct-absorption methods in the range of 439–540 GHz and Fourier transform microwave (FTMW) techniques from 9 to 39 GHz. This species was produced by the reaction of zinc vapor and chlorine gas with H₂ or D₂ in a d.c. glow discharge for the sub-millimeter studies. In the FTMW measurements, HZnCl was created in a discharge nozzle from Cl₂ and (CH₃)₂Zn. Between 5 and 10 rotational transitions were measured in the sub-millimeter regime for four zinc and two chlorine isotopologues; four transitions were recorded with the FTMW machine for the main isotopologue, each consisting of several chlorine hyperfine components. The data are consistent with a linear molecule and a ¹Σ⁺ ground electronic state. Rotational and chlorine quadrupole constants were established from the spectra, as well as an r_m⁽²⁾ structure. The Zn–Cl and Zn–H bond lengths were determined to be 2.0829 and 1.5050 Å, respectively; in contrast, the Zn–Cl bond distance in ZnCl is 2.1300 Å, longer by 0.050 Å. The zinc–chlorine bond distance therefore shortens with the addition of the H atom. The ³⁵Cl electric quadrupole coupling constant of eQq = −27.429 MHz found for HZnCl suggests that this molecule is primarily an ionic species with some covalent character for the Zn–Cl bond.     

N and Δ parity doublets in the baryon spectrum

The N and Δ excitation spectrum exhibits parity doublets, i.e. states of equal total angular momentum but with opposite parity being almost degenerate in mass. Among others, it has been suggested by L.Ya. Glozman that the parity-doublet structure may be due to effective chiral restoration.     

The microwave spectrum and structure of fulvene

The microwave spectra of four ¹³C and two monodeutero species of fulvene have been recorded and analysed. Earlier data for the parent species has also been slightly refined. The final structure which emerges for fulvene is essentially three weakly coupled ethylenic entities with bond lengths: C₁C₂ = 1.470Å C₂C₃ = 1.355Å, C₃C₄ = 1.476Å and C₁C₆ = 1.3485Å. The CH bond distances and ring angles are close to expected values.     

The a-type rotational spectrum of HNCS in the excited bending states

The microwave and millimeter wave spectra of HNCS in the three bending excited states, v₄ = 1, v₅ = 1, and v₆ = 1, have been measured. The ^qR₀, ^qR₁, and ^qR₂ branches for each of these three states and the ^qR₃ branch for the lowest excited state have been assigned. Effective rotational and centrifugal distortion constants have been determined for each vibrational and K_a-rotational sub-state. Two local resonances, caused by the Coriolis induced asymmetry interaction and a b-type Coriolis resonance, allow unambiguous confirmation of the assignment of the state v₆ = 1, the first excited state of the out-of-plane vibration.     

The microwave spectrum and structure of carbonyl fluoride

The ground state microwave rotational spectra of four isotopic species of carbonyl fluoride have been measured between 18 GHz and 77 GHz, and analyzed to obtain the quartic and some sextic centrifugal constants. The rotational constants have been used to obtain a r₀ structure and, using a harmonic force field, a r_z structure is also obtained: r_z(C---F) = 1.3166 (10) Å, r_z(C---O) = 1.1700 (26) Å.These values are considerably more precise than those of the previously estimated average structure.     

The microwave spectrum and structure of chloromethyl cyclopropane

The microwave spectra of $\text{CH}{}_2\text{CH}{}_2\text{CH}$CH₂³⁵Cl and $\text{CH}{}_2\text{CH}{}_2\text{CH}$CH₂³⁷Cl have been observed and lines assigned to the gauche form. The rotational constants in MHz and distortion constants in KHz are: C₃H₅CH₂³⁵Cl, A = 11745.65, B = 2047.274, C = 1886.622, Δ_J = 0.85, Δ_JK = ? 0.9, Δ_K = 44., δ_J = ? 0.099, δ_K = 19.1, C₃H₅CH₂³⁷Cl, A = 11691.61B = 1997.664, C = 1842.823, Δ_J = 0.7, Δ_JK = ? 64.6, Δ_K = 2400, δ_J = 0.19, δ_K = ? 67.     

The microwave spectrum and structure of chlorine isocyanate

The microwave spectra of three isotopic species of chlorine isocyanate, ClNCO, have been measured in the frequency region 8–37 GHz. Spectra have been observed for molecules in both the ground and excited vibrational states, and have yielded values for the rotational constants, inertial defects, centrifugal distortion constants, and nuclear quadrupole coupling constants for both chlorine and nitrogen. The molecule has been shown to be planar, with the following internuclear parameters: fx547-1 < (NCO) = 171° 24′ ± 1° 30′, with Cl and O trans. The principal values of the chlorine nuclear quadrupole coupling tensor were calculated, and were found to be consistent with the derived structure.     

The microwave spectrum and structure of chloryl fluoride

The microwave spectra of three isotopic species of chloryl fluoride, FClO₂, in its ground vibrational state, have been measured in the frequency region 8–37 GHz. The spectra have yielded values for the rotational constants, centrifugal distortion constants, and chlorine nuclear quadrupole coupling constants, as well as the molecular dipole moment, 1.722 ± 0.03 D. The molecule has been shown to have C_s symmetry, and a pyramidal configuration, with the chlorine atom at the apex of the pyramid. The following internuclear parameters were obtained:r(Cl?F)1.697±0.003 A r(Cl?F)=1.418±0.002AThe structural parameters, quadrupole coupling constants, dipole moment and force field are explained in terms of a bonding scheme in which a fluorine 2p atomic orbital overlaps with the highest occupied orbital of ClO₂; there is considerable evidence for withdrawal of electron density from this singly occupied antibonding orbital of ClO₂ toward the fluorine atom.     

The microwave spectrum of trifluoroacetonitrile in excited vibrational states

The microwave transitions J → J + 1 have been observed in the symmetric top molecule trifluoroacetonitrile, CF₃CN, for molecules excited into several of the low-lying vibrational states. Measurements made in the degenerate states v₇ = 1 v₈ = 1 have been fitted to the formula derived by Grenier-Besson and Amat (1) for transitions J → J + 1 in degenerate vibrational states of molecules with C_3v symmetry. The measurements for the state v₈ = 1 have been extended to 150 GHz where it is shown that the above formula becomes inadequate to describe accurately the observed spectrum.     

Excited states and photochemistry of saturated molecules. The vibrational structure in the electronic spectrum of ethane

Ab initio wavefunctions including single excitation CI are used to analyze the origin of the vibrational structure in the low-energy band of the electronic spectrum of ethane. The calculations suggest that the vibrational structure appears to be due to the overlapping progressions from two vertical states (1E_u and 1A_2u), both of which are unstable to distortion to C_2h symmetry, wherein they are characterized by significantly lengthened CC bonds.     

The microwave spectrum and structure of the argon trifluoroacetonitrile complex

The rotational spectrum of argon trifluoroacetonitrile complex has been studied by pulsed-nozzle, Fourier transform microwave spectroscopy. Both a-type and b-type transitions have been observed. The rotational constants are A = 3053.0903(2) MHz, B = 1039.9570(2) MHz, and C = 895.5788(1) MHz. The ¹⁴N nuclear quadrupole hyperfine components of the rotational transitions have been resolved, the ¹⁴N nuclear quadrupole coupling constants are χ_aa = 1.746(1) MHz, and χ_bb − χ_cc = −6.426(2) MHz. The complex is T-shaped, with the argon atom located 3.73 Å from the center of mass of the trifluoroacetonitrile molecule.     

The microwave spectrum of piperidine: Equatorial and axial ground states

The microwave spectra of piperidine and N-deuterated piperidine were investigated between 8 and 40 GHz. The ground states of both equatorial and axial conformers have been identified by both type-A and type-C transitions, and the substitution coordinates of the imino hydrogen have been determined for both conformers. Dipole-moment components for the equatorial conformer are μ_a = 0.178 D, μ_c = 0.80 D, μ = 0.82 D, and for the axial conformer are μ_a = 1.07 D, μ_c = 0.521 D, μ = 1.19 D. The quadrupole coupling constants for the axial conformer are: χ_aa = ?3.80 MHz, χ_bb = 2.91 MHz, χ_cc = 0.83 MHz and for the equatorial conformer χ_cc = ?4.83 MHz. The rotational constants indicate a significant flattening of the ring in axial piperidine compared with equatorial piperidine. The equatorial conformer is the more abundant; intensity measurements on several sets of lines indicate the excess energy of the axial conformer to be 3.1 ± 0.3 kJ mole^?1. This represents a significant change from our earlier reported value and is now more in line with measurements obtained by other methods.     

The microwave spectrum of cyanoacetylene in ground and excited vibrational states

Microwave transitions are reported for ten isotopic species of cyanoacetylene in the ground, v ₄, v ₆, v ₆ and v ₇ vibrational states in the region 26·5-40·0 GHz. In addition millimetre-wave transitions of HCCCN and DCCCN in the ground v ₅, v ₆ and v ₇ vibrational states in the region 54·5-211·8 GHz have been measured. The combined data have been analysed to yield B_v, D_v, γ_rs, γ_ltlt′ and q_t vibration-rotation parameters, for HCCCN and DCCCN.

In addition millimetre-wave measurements pertaining to the v ₆ + v ₇ and v ₅ + v ₇ vibrational states have been analysed to give values for r_tt′J and approximate values of g_tt′ and r_tt′ (t = 5, 6; t′ = 7).

Rotational constants B_v in the first excited state of the fundamental vibrations v ₄, v ₅, v ₆ and v ₇ are combined with infra-red values for v ₁, v ₂ and v ₃ to give B_e for both HCCCN and DCCCN.     

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5-18.5 GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2 GS/s arbitrary waveform generator as a frequency source and a 12 GHz digital oscilloscope to digitize the down converted molecular free induction decay (FID). Signal averaging in the time domain is used to increase the signal-to-noise ratio. The rotational constants of three unique conformers of epifluorohydrin were measured, as well as the rotational constants of the three unique ¹³C isotopomers and the ¹⁸O isotopomer (in natural abundance) of the most stable conformer. The rotational constants of the two less stable conformers differ significantly from those previously reported [F.G. Fujiwara, J.L. Painter, H. Kim, J. Mol. Struct. 41 (1977) 169-175]. Ab initio calculations were performed for all three conformations and are compared to experimental values.     

Isotope dependence of the rotational constant of sulfur monoxide in the 3Σ-ground state

The rotational spectra of ³²S¹⁶O, ³⁴S¹⁶O and ³²S¹⁸O were measured. The rotational constant B₀ was accurately determined for all three isotopes whereas the spin-spin coupling λ₀ and the spin-rotation coupling γ₀ have less accuracy due to the strong correlation of these constants for the observed transitions. The evaluated breakdown of the Born-Oppenheimer approximation can primarily be attributed to the nonadiabatic correction term found for ¹Σ-diatomic molecules. The small adiabatic correction for SO is obtained with the opposite sign as usually derived in ¹Σ-molecules.     

The rotational spectrum and hyperfine structure of arsenic monophosphide, AsP

Arsenic monophosphide has been prepared by laser ablation of arsenic in the presence of PH₃. The J = 2-1 and 1-0 transitions in both the ground and first excited vibrational states have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. An improved equilibrium internuclear distance (r_e) has been obtained. Hyperfine structure in the rotational spectrum of AsP has been resolved and has led to the first determinations of the As nuclear quadrupole coupling constant and both nuclear spin-rotation constants. The data enable the electronic structure of AsP to be compared with those of other mixed Group 15 diatomic molecules.     

Microwave spectrum and hyperfine structure in the rotational spectrum of diatomic gallium iodide

The J = 3←2 rotational transition of diatomic GaI molecule has been measured in the microwave region. The molecules were produced by a reaction of gallium and lead iodide in the heated zone of a splitted wave guide. The lines were observed in the 10-GHz frequency region at a reaction temperature 270–350°C. Molecular parameters have been derived for ⁶⁹Ga¹²⁷I and ⁷¹Ga¹²⁷I from the analysis of the hyperfine structure. Systematic variations in quadrupole coupling constants in III_a halides have been observed. Vibrational dependence of the nuclear quadrupole interaction for ⁶⁹Ga¹²⁷I can be written as follows: $\text{eq}{}_{\mathrm{<mtext>v</mtext>}}\text{Q(}{}^{69}\text{Ga}\text{) = ?81.29(25) + 0.43(30)(v +}\text{1}\text{2}\text{)}\text{MHz}$, $\text{eq}{}_{\mathrm{<mtext>v</mtext>}}\text{Q(}{}^{127}\text{I}\text{) = ?369.35(10) ? 2.54(16)(v +}\text{1}\text{2}\text{)}\text{MHz}$.     

The electronic spectrum of PrO. Energy linkages,rotational analysis,and hyperfine structure for systems XVII and XXI

Doppler-limited laser excitation spectra for four bands of PrO have been recorded: System XvII 0-0, System XXI 0-0 and 0–1, and the 0-0 intercombination between the upper and lower states, respectively, of Systems XVII and XXI. First lines in R and P branches prove that Systems XVII and XXI are, respectively, $\text{Ω}\text{′ = 4.5 ?}\text{Ω}\text{″ = 3.5}$ and $\text{Ω}\text{′ =}\text{Ω}\text{″ = 4.5}$. Hyperfine components are well resolved for all four excitation bands. Rotational and hyperfine constants are determined by least-squares fits of data from all four bands together. In addition, fluorescence spectra, recorded from various J′, v′ = 0 levels of the upper states of Systems XVII and XXI, reveal five new low-lying states. Principal constants (in cm^?1) for nine $\text{Ω-states}$ follow (1σ uncertainty in parentheses):

     

State	$\text{T}{}_{\mathrm{v}}$	$\text{B}{}_{\mathrm{v}}$	$\text{d}\text{(hfs)}$
$\text{Ω′ = 4.5 (System XXI)}$	18 882.388 (2)	0.353001 (18)	0.12403 (71)
$\text{Ω′ = 4.5 (System XVII)}$	16 594.075 (1)	0.353736 (20)	0.12977 (67)
$\text{Ω}\text{″ = 3.5}$	3 887.15 (16)	0.35751 (28)	—
$\text{Ω}\text{″ = 3.5}$	2 931.66 (15)	0.35712 (21)	—
$\text{Ω}\text{″ = 4.5}$	2 155.16 (30)	0.36264 (67)	—
$\text{Ω}\text{″ = 5.5}$	2 099.16 (31)	0.35079 (71)	—
$\text{Ω}\text{″ = 3.5}$	2 064.34 (13)	0.35654 (20)	—
$\text{Ω″ = 4.5 (System XXI)}$	217.383 (1)	0.362134 (20)	0.27744 (66)
$\text{Ω″ = 3.5 (System XVII)}$	0.0	0.360948 (16)	?0.00809 (85)