Frequency measurements in the 10 μm spectrum of 11BCl3

This paper presents a study of the spectroscopy of ¹¹BCl₃ using the Doppler-free saturated absorption technique. Many lines in the degenerate ν₃ fundamental of this molecule have been recorded using the 10P branch of a carbon dioxide laser. The absolute frequencies of the linecentres of these absorptions have been measured to an accuracy of better than 10 kHz, using frequencies calibrated against transitions in SF₆ and OsO₄. Hyperfine structure due to the Cl nuclei was easily resolved, and more detailed structure, which may be attributed to the ¹¹B quadrupole interaction, was also seen. The splittings between individual quadrupole components were measured to an accuracy of better than 2 kHz where SF₆ references were used, and to about 8 kHz in the case of OsO₄. Peak-to-peak linewidths as low as 22 kHz have been recorded, representing the highest resolution data yet obtained for this molecule.     

Bound state spectrum from the light-cone two-body equation in φ3-theories

The relativistic bound state problem with the light-cone two-body equation (i.e. Bethe-Salpeter equation in the infinite momentum frame) is investigated in the light-cone ladder approximation to φ³-theories. A variational principle is found for the eigenvalues. Numerical results are compared with some existing calculations and with some new analytic results.     

The rotational spectrum of the SH radical in its XΣ state

All the available data on the rotational energy levels of the SH⁺ (sulfoniumylidene) radical in the v = 0 and 1 levels of the X³Σ⁻ ground state have been subjected to a single, weighted least-squares fit to determine an improved set of molecular parameters for this molecule. The results have been used to calculate the rotational spectrum of the SH⁺ radical in the v = 0 and 1 levels up to the N = 4-3 transition.     

Intensities of two-photon transitions in the 2ν2 band of NH3

We determine theoretically all the coincidences between the ¹⁴NH₃ν₂= 0−2 band and the spectrum of two CO₂ lasers; they can be induced either by a small frequency tuning of lasers or by a Stark tuning of molecular levels. For each two-photon transition we report the line intensity, the preferred laser lines and the necessary Stark field or laser tuning. The theoretical line intensities are compared to the results of an optoacoustic Doppler-free experiment.     

Millimeter-wave spectrum of the C4v molecule IOF5: l-type doubling of the kl = −1 transitions in the v11(E) = 1 state spectrum

Measurements of the rotational spectrum of the C_4v molecule IOF₅ are reported for the excited vibrational state v₁₁(E) = 1 for the transitions J13 ← 12, 14 ← 13, 16 ← 15, and 17 ← 16 (55–72 GHz) including the observation of the kl = −1 (q⁻), l-doubling effect. Detailed assignments of the E-state spectrum are presented based on the overlapping quadrupole structure. These data are analyzed together with earlier results for the excited vibrational state v₆(B₁) = 1 to give information concerning the ν₆(B₁)-ν₁₁(E) Coriolis interaction and the (Δl, Δk) = (2, 2) (q⁺) and (2, −2) (q⁻)l-resonance interactions. It is found that q₁₁⁻ = −2.57(10) MHz, |q₁₁⁺| = 0.094(20) MHz, Δ = ν₆ − ν₁₁ = 45.2(7) cm⁻, ζ_11,11^z = +0.18(1) and |ζ_6,11^y| = 0.73(4).     

The overtone spectrum of carbonyl sulfide in the region of the ν1+4ν3 and 5ν3 bands by ICLAS-VECSEL

The high-resolution overtone spectrum of OCS has been recorded in the region of the ν₁+4ν₃ and 5ν₃ bands by intracavity laser absorption spectroscopy based on an optically pumped vertical external cavity surface emitting laser (VECSEL). The extremely weak ν₁+4ν₃ band at was found to be isolated. The 5ν₃ band at is accompanied by two weaker bands at 9933.53 and assigned to the 12⁰4-00⁰0 and 04⁰4-00⁰0 bands, respectively. In addition, the 01¹5-01¹0 hot band was detected together with the extremely weak band heads of the R branch of the 02^0,25-02^0,20 hot bands. Finally, the 5ν₃ band of the ¹⁶O¹²C³⁴S minor isotopomer, present in natural abundance in the sample, was also observed and rotationally analyzed. Effective state parameters could be retrieved by standard band-by-band rotational fitting of the line positions, leading to a typical rms of . The observed line positions were compared to the predictions of the global model described by Rhaibi et al. [J. Mol. Spectrosc. 191 (1998) 32-44]. In general, the agreement is excellent, close to the experimental uncertainty () thus confirming the high predictive ability of this effective Hamiltonian model. Weak but significant deviations up to were, however, identified for two rotational levels of the highly excited 2,16⁰,0 dark state, observed through a local interaction with the 00⁰5 state. In the case of the ¹⁶O¹²C³⁴S isotopomer, the predicted line wavenumbers of the 5ν₃ band were globally overestimated by about . The new data have been included in the corresponding global model, leading to almost unchanged values of the molecular parameters and a statistical agreement with the experiment.     

Low-temperature high-resolution absorption spectrum of 14NH3 in the ν1+ν3 band region (1.51 μm)

Jet-cooled spectra of ¹⁴NH₃ and ¹⁵NH₃ in natural abundance were recorded using cavity ring-down (CRDS, 6584–6670 cm^?1) and cavity enhanced absorption (CEAS, 6530–6700 cm^?1) spectroscopy. Line broadening effects in the CRDS spectrum allowed lines with J ^″-values between 0 and 3 to be identified. Intensity ratios in ¹⁴NH₃ between the jet-cooled CRDS and literature room-temperature data from Sung et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012 K. Sung , L.R. Brown , X. Huang , D.W. Schwenke , T.J. Lee , S.L. Coy , and K.K. Lehmann , J. Quant. Spectrosc. Radiat. Transfer 113 , 1066 (2012).[Crossref], [Web of Science ®] , [Google Scholar]), 1066) further assisted the line assignments. Ground state combination differences were extensively used to support the assignments, providing reliable values for J, K and inversion symmetry of the ground state vibrational levels. CEAS data helped in this respect for the lowest J lines, some of which are saturated in the CRDS spectrum. Further information on a/s doublets arose from the observed spectral structures. Thirty-two transitions of ¹⁴NH₃ were assigned in this way and a limited but significant number (19) of changes in the assignments results, compared to Sung et al. or to Cacciani et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012 P. Cacciani , P. Cermak , J. Cosleou , M. Khelkhal , P. Jeseck , and X. Michaut , J. Quant. Spectrosc. Radiat. Transfer 113 , 1084 (2012).[Crossref], [Web of Science ®] , [Google Scholar]), 1084). Sixteen known and 25 new low-J transitions were identified for ¹⁵NH₃ in the CRDS spectrum but the much scarcer literature information did not allow for any more refined assignment. The present line position measurements improve on literature values published for ¹⁵NH₃ and on some line positions for ¹⁴NH₃.     

On the L3 level photoelectron spectrum of Cu metal measured in coincidence with the L3–VV Auger-electron spectrum

We provide an answer to the question why the L₃ photoelectron line of Cu metal measured in coincidence with the L₃–VV (³F or ¹G) Auger-electron line, does not line up with the L₃ single photoelectron line. We provide also an answer to the question why the L₃ coincidence photoelectron line is unshifted when the Auger-electron analyzer is moved away from the Auger-electron line. We show that it is the initial core–hole self-energy by the monopole excitation (screening) and the density of final states which play an important role in the shift and narrowing of Auger-photoelectron coincidence spectroscopy (APECS) spectral line. To explain the shifted APECS spectral line, Thurgate and Jiang (Surf. Sci. 466 (2000) L807) recently proposed the presence of two different core–hole states in the main-line state upon the L₃ level ionization in Cu metal. However, their explanation appears to be incorrect.     

Frequency measurements in the 9μm spectrum of CF3Br

Carbon dioxide laser saturation spectra of CF₃ Br have been explored with a view to hyperfine spectroscopy and references for frequency standards in the 9μm band of the carbon dioxide laser. Spectra have been obtained using the laser transitions 9R(16)-9R(30). and show many saturation features in each case. Several of the stronger features have been referenced directly to CO₂ frequencies with an estimated accuracy of 25 kHz. Spacings between the hyperfine components are also reported. This work represents some of the first data relevant to 9μm locking to molecular absorptions.     

Reanalysis of the photoassociation spectrum of 133Cs2 （6P3/2） lg state

Reanalysis of the photoassociation spectrum of the weakly binding （6S1/2 ＋ 6P3/2） lg 133Cs2 levels, reported in the previous study [J. Mol. Spectro. 255 （2009） 106], is performed by using a Lu-Fano graph coupled to the improved LeRoy- Bernstein formula including two additional modified terms. A more accurate coefficient （c3） is obtained for the leading long-range potential （-c3/R3） of a diatomic molecule.     

Observation of forbidden transitions in the ν4 band of NH3: corrections to the ground state ΔK = 3 intervals

This paper presents a preliminary evaluation of the C rotational constant and coefficients of the operators P_z ²ⁿ up to n = 4 for NH₃ in the ground state. These constants are evaluated on the basis of the determination of 14 different ΔK = 3 ground state intervals obtained from measurement of many Δ(K - l) = 3 transitions observed in the ν₄ vibration rotation band. Corrections to the ground state term values for NH₃ are given as a function of K, thus permitting ΔK = 3 transitions to be determined with accuracies comparable to those of normal allowed transitions. The perturbation which gives rise to the observed transitions is large, but has not been treated in previous analyses of the ν₄-2ν₂ bands.     

Analysis of the stimulated Raman spectrum of the ν16ν2 + ν18 Fermi dyad of benzene

Ionization-detected stimulated Raman spectroscopy was used to obtain high-resolution recordings of the two perpendicular bands of the benzene molecule centered at 1591.327 and 1609.518 cm⁻¹. The effective resolution was further enhanced by deconvolving the spectrum to a linewidth 0.003 to 0.004 cm⁻¹. Fine-tuning of the ionizing radiation made it possible to record the transitions belonging to each band separately, thus greatly simplifying the spectrum in the region of overlap. The strong ^sS and ^oO branches were, for the most part, completely resolved as were many lines in the weaker ^oP and ^sR branches and even in the central ^oQ and ^sQ branches. The observed bands belong to the E_2g fundamental ν₁₆ in nearly exact Fermi resonance with the combination ν₂ + ν₁₈. A detailed rovibrational analysis of the spectrum is reported. A perturbation detected in the ^sS_k branches of the lower-frequency band for K = 19 to 23 was identified as a quintic anharmonic resonance with the third overtone, 4ν₂₀, of the lowest lying fundamental ν₂₀, which is infrared- and Raman-inactive (species E_2u). Deperturbed spectroscopic constants for the interacting states are reported which reproduce the observed line positions with a standard deviation of 0.0013 cm⁻¹. The unperturbed origins of the ν₁₆ and ν₂ + ν₁₈ states are only 1.106 cm⁻¹ apart. The fundamental ν₁₆ was identified with the higher-frequency state with origin at 1600.976 cm⁻¹.     

High resolution vibration-rotation spectrum of the D2O molecule in the region near the 2ν1 + ν2 + ν3 absorption band

The high resolution Fourier transform spectrum of the D₂0 (ν = ν₁ + ν₂/2 + ν₃ = 3.5) polyad was analysed within the framework of the Hamiltonian model taking into account resonance interactions between the seven states (310), (211), (112), (013), (230), (131) and (032). Transitions belonging to the 2ν₁ + ν₂ + ν₃, 3ν₁ +ν₂ and 3ν₂ + 2ν₃ bands were assigned in the experimentally recorded spectrum. This provided the possibility of obtaining spectroscopic parameters of the ‘visible’ states (211), (310) and (032) and of estimating the band centres, and the rotational and resonance interaction parameters of the ‘dark’ states (112) and (131).     

Similarity of the Fermi surface in the hidden order state and in the antiferromagnetic state of URu₂Si₂

Shubnikov-de Haas measurements of high quality URu2Si2 single crystals reveal two previously unobserved Fermi surface branches in the so-called hidden order phase. Therefore, about 55% of the enhanced mass is now detected. Under pressure in the antiferromagnetic state, the Shubnikov-de Haas frequencies for magnetic fields applied along the crystalline c axis show little change compared with the zero pressure data. This implies a similar Fermi surface in both the hidden order and antiferromagnetic states, which strongly suggests that the lattice doubling in the antiferromagnetic phase due to the ordering vector Q(AF)=(001) already occurs in the hidden order. These measurements provide a good test for existing or future theories of the hidden order parameter.     

The infra-red L.M.R. spectrum of SeH in the X 2Π state

Magnetic dipole transitions between the ²Π_1/2 and ²Π_3/2 components of the ground state of SeH have been observed at about 1780 cm^-1 in a L.M.R. experiment using a CO laser. Transitions have been detected for the four most abundant natural isotopes of Se. The transition frequencies depend primarily on the magnitude of the spin-orbit coupling constant and have been analysed in conjunction with data from the E.P.R. spectrum to yield

The admixture of other electronic states by spin-orbit coupling has been investigated to third order in perturbation theory and found to produce significant effects.     

Dust Charging in Electronegative SiH4 Plasmas

We theoretically investigate the dust charging in electronegative silane (SiH4) plasmas, taking into account the effects of UV photodetachment. It is found that UV photodetachment could significantly lower the dust negative charge and even makes dust grains be positively charged under some special conditions. In addition, the other parameters, involving the negative ion and dust number densities, electron temperature and dust radius, have great effects upon the dust charging.     

On experimental tests of D-states in the 3He3H ground state

Recent experiments relevant for D-state components in the ground state of the A = 3 systems are discussed in a simple scheme. This displays the close connection between the tensor force and the D-state components and allows one to interpret the experimental results in a transparent way. Suggestions for a complete experimental test of the D-state are given.