THz spectroscopy of H2D

The 2₁₂ − 1₁₁ line of H₂D⁺ at 2.363 THz that was detected toward Sgr B2 and identified based on a calculated line frequency has been measured in the laboratory precisely by using a tunable far-infrared spectrometer. All the available THz lines and known millimeter- and submillimeter-wave lines together with the combination differences derived from the infrared transitions are fitted to the Watson effective Hamiltonian. A set of improved molecular constants are obtained.     

Submillimeter-wave spectroscopy of HN2 and DN2 in the excited vibrational states

The pure rotational transitions of HN₂⁺ and DN₂⁺ in the first excited vibrational states for all the fundamental vibrational modes have been observed in the range of 300-750 GHz. The molecular constants determined are much more accurate compared with those obtained from the infrared spectroscopy. The equilibrium rotational constants, B_e = 46832.45 (71) MHz for HN₂⁺ and B_e = 38708.38 (58) MHz for DN₂⁺, have been determined by correcting for the higher-order vibration-rotation interaction effects, γ_ij, obtained by an infrared investigation. The equilibrium bond lengths are derived from these equilibrium rotational constants: r_e(H-N) = 1.03460 (14) Å and r_e (N-N) = 1.092698 (26) Å.     

Lyman transitions of high rovibrationally excited H2, HD and D2 molecules

Energies and probabilities of Lyman transitions of high rovibrationally excited H₂, HD and D₂ molecules have been measured and compared with calculations. The experimental results are obtained from laser-induced fluorescence spectra that have been recorded in the spectral range from 60 500 to 83 500 cm⁻¹, covering 2/3 of the hydrogen Lyman band system. The necessary vacuum-UV radiation is produced by stimulated anti-Stokes Raman scattering, providing a widely tunable radiation source with narrow spectral bandwidth to resolve single Lyman transitions. The highest internal energies of detected hydrogen isotopologues are close to the dissociation limit. This extends the available data base of Lyman transitions from and to higher rotational states (J > 10) of HD and D₂.     

The microwave spectra of ortho-fluorotoluene with the asymmetric internal rotors CH2D and CD2H

The rotational spectra of αd₁- and αd₂-ortho-fluorotoluene in the ground state of the methyl group torsion have been measured. The evaluation of the spectra has been based on the theory for the internal rotation of an asymmetric internal top formulated earlier by several authors. The barrier potential being threefold symmetric (V₃), each torsional level consists of three nondegenerate substates, designated as sy and ±asy. The sy-state is assigned to the conformation with the unique methyl hydrogen isotope within the molecular heavy-atom plane (sy-rotamer), while the ±asy-states belong to the respective out-of-plane conformation (asy-rotamer). In the torsional ground state the level spacing between the ±asy substates is very small and numerous accidental close degeneracies are present between the rotational level systems based on these torsional substates. The rotational levels involved are strongly perturbed by the coupling between molecular overall rotation and internal rotation. Large deviations from a rigid rotor spectrum and (+) ? (?) intersystem (“tunneling”) transitions are observed. The spectrum of the asy-rotamer can be well reproduced by a “two-dimensional” Hamiltonian containing 11 “rotational constants,” 9 of which are determined by a fit to the spectrum. Several are sufficiently barrier-dependent to derive V₃. We obtain (in cal/mole) 567 ± 48 for αd₁-ortho-fluorotoluene, 711 ± 40 for the αd₂-isotope. The deviations from 649 cal/mole for the normal isotope are appreciable, probably indicating shortcomings of the semirigid model. The sy-rotamer presents a rigid rotor spectrum.     

Photoelectron angular distributions from H2 and D2

The photoelectron asymmetry parameters of H₂ and D₂ have been measured using synchrotron radiation over the photon energy range 19–27 eV. The results are compared with previous measurements and several theoretical calculations. A few of the theoretical calculations are in good agreement with experiment, but most of them predict asymmetries which are too large. Essentially identical β values were measured for H₂ and D₂. This result is discussed in terms of differences which could arise due to vibrational and rotational structure.     

Fourier transform infrared spectra of H2CS and D2CS

Infrared spectra of thoformaldehyde, H₂CS and D₂CS, were observed in the gas phase at a resolution of better than 0.1 cm^?1 from 4000 to 400 cm^?1 using a Nicolet FTIR system. Vibrational band origins and rotational constants were determined for ν₂, ν₃, ν₄, and ν₆ of H₂CS and for ν₁, ν₂, ν₃, ν₄, and ν₆ of D₂CS. The ν₃, ν₄, and ν₆ bands of H₂CS were analyzed as a set of three Coriolis interacting bands, and three Coriolis constants were determined; similarly the ν₄ and ν₆ bands of D₂CS were analyzed as a pair of interacting bands and one Coriolis constant was determined. A general harmonic force field was determined, without constraints, to fit the vibrational wavenumbers, Coriolis constants, and centrifugal distortion constants. A zero-point (r_z) structure was determined from the ground-state rotational constants, and the equilibrium (r_e) bond lengths were estimated.     

Penning ionization electron spectroscopy of H2O,D2O,H2S and SO2

Electron energy peak shifts and peak shapes were determined in the ionization of H₂O, D₂O, H₂S and SO₂ by Ne(³P₂) and He(2¹S, 2³S) metastable atoms. The shifts are large, especially in ionization of H₂O and D₂O into the ionic ground state and are probably mostly due to chemical interaction during the collision.In a previous paper the electron energy distribution curves for ionization of CO, HCl, HBr, N₂O, NO₂, CO₂, COS and CS₂ by helium, neon and argon metastables and the characteristics of this ionization were described¹. In this paper the series of triatomic molecules was extended to the molecules H₂O, D₂O, H₂S and SO₂. Because all these molecules have considerable dipole moments it could be expected that the peak shifts might be enhanced as compared with other triatomic molecules.     

Mass spectroscopy of HCN-laser plasmas with H2 and D2

Mass spectroscopic studies reveal the role of H₂ in HCN-laser plasma. This is confirmed by laser experiments with different gas mixtures containing H₂ and D₂.     

ΔK = 2 transitions in H2CO and D2CO

Weak transitions of the type ΔJ = ± 1, $\text{Δ}\text{K}{}_{\mathrm{a}}\text{= ? 2}$, ΔK_c = ± 3 have been observed in H₂CO and D₂CO by the millimeterwave double resonance method and also by direct absorption with a Stark modulated spectrometer. The addition of these new transitions in a least-squares analysis, in which all previously known microwave and millimeterwave data are also included, results in an improved set of rotational and distortion constants.     

Millimeter-wave spectroscopy of deuterated hydrogen sulfide, SH2D

The monodeuterated isotopologue of the sulfonium ion, the asymmetric species SH₂D⁺, was produced in a magnetically confined negative glow discharge and detected for the first time by means of its rotational spectrum in the region 324-637 GHz. The determined rotational constants, along with those for the symmetric isotopologues and for obtained in previous measurements, enabled to compute a semi-experimental equilibrium structure, where the contribution of the zero-point vibrations is assumed from available ab initio calculations. In addition, thanks to the large body of quartic centrifugal distortion constants now available, the harmonic force field of the sulfonium ion has been refined by a least-squares procedure.     

Calculated spectroscopic properties for C12H and HC11N, molecules of astrochemical interest

A comparative theoretical study of the (potential) interstellar molecules C₁₂H⁻ and HC₁₁N has been carried out, making use of the coupled cluster variant CCSD(T) in conjunction with large basis sets comprising up to 715 contracted Gaussian-type orbitals. The ground-state rotational constants of C₁₂H⁻ and C₁₂D⁻ are predicted to be 174.11 and 170.32 MHz, respectively. The corresponding quartic centrifugal distortion constant of C₁₂H⁻ is estimated to be 0.26 Hz, to be compared with an experimental value of 0.24 Hz for HC₁₁N. Most of the total infrared intensity of C₁₂H⁻ isotopomers concentrates in one or two bands around 2000 cm⁻¹. The total IR intensity exceeds 13 000 km mol⁻¹ and is thus about 20 times larger than for HC₁₁ N isotopomers. The bending vibrations of C₁₂H⁻, HC₁₁N and their deuterated species are analysed by means of mass plots.     

Intensity dependent polarization change in the D1 and D2 resonance lines of sodium

Intensity dependent polarization change and rotation of elliptically polarized light are observed and analyzed in the D₁ and D₂ resonance lines of sodium. The characteristics of these effects in terms of the difference between self- and cross- saturation coefficients are discussed for transitions with arbitrary values of total angular momentum J.     

Far-infrared absorption intensities of H2O and D2O in C6H6

Far-i.r. absorption intensities have been measured for H₂O and D₂O in C₆H₆ solutions. Beer's law plots were found to be nonlinear. From the plots, the equilibrium constants of dimer formation in benzene were estimated to be 2.4M^-1 and 3.3M^-1 for H₂O and D₂O at 20°C, respectively. Based on Onsager's reaction field and including explicitly the effect of differences in molecular size between solute and solvent molecules, the internal moment of a water molecule and the volume ratio of a molecule to a cavity were estimated from the integrated absorption intensity of a D₂O monomer in C₆H₆ as 1.98 D and 0.7, respectively     

Interaction of PH3 coadsorbed with H2, D2, O2 and H2O on Rh(100)

The coadsorption of PH₃ with H₂, D₂, O₂ and H₂O on Rh(100) has been studied using temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The adsorption and molecular desorption of PH₃ is not affected by preadsorbed H₂, D₂ and O₂. Preadsorbed PH₃ blocks H₂ desorption sites while postdosed PH₃ displaces H₂ (D₂₁) from the Rh(100). When D₂ and PH₃ are coadsorbed, no D appears in desorbed phosphine. Preadsorbed O₂ reduces the amount of H₂ desorption (from PH₃ decomposition) and increases the H₂ desorption temperature. There is also some reaction between O(a) and H(a) to form water. Preexposure to H₂O decreases the extent of PH₃ adsorption and of PH₃ decomposition.     

H NMR study of N(CH3)4H(ClF2CCOO)2

The proton spin–lattice relaxation times and ¹H NMR second moments were measured over a wide range of temperature. The results were compared with those of the ¹⁹F NMR relaxation that we obtained earlier. For both nuclear species, the evolution of the longitudinal magnetizations with time is observed to be strongly bi-exponential and were in good quantitative agreement with the cross-relaxation theory.     

Study of the luminescence of H2O and D2O ices induced by charged-particle bombardment

We measured the optical emission of H₂O and D₂O ices in visible region (300-500 nm) induced by energetic hydrogen ions (H⁺, H₂⁺, and H₃⁺) irradiation. Our analysis of the data of ion-stimulated luminescence (ISL) shows that all spectra of ISL emission are identical, independent of projectile. We show that all lines in the ISL emission spectrum may be assigned to decays from excited particles and/or fragments of H, H₂, OH, and H₂O. From the independence of emission spectrum on projectile we conclude that the final process causing the emissions may be attributed to the interaction between H⁺ (and/or H) and the water molecules.     

The absorption cross sections of H2 and D2 from 180 to 780 Å

The absolute photoabsorption cross sections of H₂ and D₂ have been measured photoelectrically in the wavelength region from 180 to 780 Å using synchrotron radiation. At photon wavelengths shorter than 650 Å, the absorption cross section was found to be structureless and to decrease montonically with decreasing wavelength. In this spectral region, both gases have nearly equal absorption cross sections, varying only within the experimental error. At photon wavelengths greater than λ 650 Å, structure is evident in the cross section of both gases and presumably corresponds to the Rydberg States reported by various authors.     

Theoretical study of stereodynamics for the N+H2/D2/T2 reactions

The effects of isotopic variants on stereodynamic properties for the title reactions have been investigated using a quasi-classical trajectory method based on the first excited state NH2（I^2A＇） potential energy surface [Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644]. The forward–backward symmetry scattering of the differential cross section can be observed, which demonstrates that all these reactions follow the insertion mechanism. Three angle distribution functions P（θr）, P（φr）, and P（θr, φr） with different collision energies and target molecules H2/D2/T2 are calculated. It is shown that the product rotational angular momentum is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The title reaction is mainly governed by the ＂in-plane＂ mechanism through the calculated distribution function P（θr, φr）. The observable influences on the rotational polarization of the product by the isotopic substitution of H/D/T can be demonstrated.