Calculation of the influence of the wind effect and collision-induced velocity changes on the H2O-molecule absorption-line profiles upon broadening by monatomic gases

The influence exerted on the H₂O-molecule absorption line profiles in the H₂O-He, H₂O-Ar, and H₂O-Kr systems by two factors—the dependence of broadening coefficient γ on velocity ν _a of the absorbing H₂O molecule (wind effect) and the collision-induced change in the H₂O molecule velocity—is studied. Three H₂O molecule absorption lines of the ν ₂ band, which are formed by transitions from energy levels with different rotational quantum numbers J and K _a , are chosen for investigations.     

The decay of174Ta

Levels in¹⁷⁴Hf excited in the decay of¹⁷⁴Ta have been studied. Measurements of gamma-rays, conversion electrons and gamma-gamma-time coincidences were performed. The ground state band, the beta-vibrational band, the gamma-vibrational band with its head at 1226.81 keV, aK=3⁺ band at 1303.42 keV and aK=2^? octupole band at 1308.67 keV were observed. Several 2⁺ levels withK=0 are excited. The mainβ ⁺-branches proceed through allowed or first-forbidden transitions to the 2⁺ and 4⁺ levels of the ground state band. The character of theI ^π=3⁽⁺⁾ ground state of¹⁷⁴Ta is discussed.     

Niveaux d'énergie et spectres de rayons X du rutile

The electronic levels of the complex TiO^?8₆ in the D_2h symmetry are determined according to an extended L. C. A. O. method. The results can explain the X-ray spectra of TiO₂. The absoption L_III and K rays are related to transitions from the 2p_3/2 and 1 s levels to the conduction band levels since the emission L_III and K components are explained by the transitions from the valence band levels to the 2p_3/2 and 1 s states. Interband transitions are related to the components of the optical reflexion spectrum of TiO₂ for the energies 0–20 eV. A comparaison is made with the electronic band structures of SnO₂, TiO₂ and BaTiO₃. At the center of the Brillouin zone, we obtain a forbidden gap of 3,01 eV, the corresponding widths of the valence and conduction band are 4,8 and 2,9 eV.     

Rotational analysis of the 7390- and 7937-Å bands of NO2 by means of Fourier transform spectroscopy

We have extended to higher N and to K_a = 3 and 4 the rotational analysis of the 7390-Å band of NO₂ performed by K. E. Hallin and A. J. Merer (Canad. J. Phys.55, 2101–2112 (1977)). The lines belong to a perturbed parallel band for which Hallin and others have proposed the vibrational assignment (2 13 1)-(0 0 0) within the electronic ground state. These authors presumed that this band borrows its intensity through a vibronic coupling (spin-orbit and/or Coriolis coupling) from the stronger (0 2 0)-(0 0 0) band of the $\text{A}\text{?}\text{-}\text{X}\text{?}$ electronic system at 7460 Å. We have observed about 900 transitions belonging to the K_a = 0, 1, 2, 3, 4 subbands of the (2 13 1)-(0 0 0) band for N values going up to about 23, and 300 lines of the “hot” band (2 13 1)-(0 1 0). We have also looked for spin-orbit-induced transitions and we have detected about 400 transitions with ΔN ≠ ΔJ. Among them ΔN = ±2 transitions with ΔK_a = 0 or ± 2 have been observed, indicating that N and K_a are no longer good quantum numbers, and demonstrating clearly the existence of rovibronic interactions perturbing the upper levels of the transitions.     

Identification of forbidden vibration-rotation transitions in 15NH3

Forbidden Δ|k ? l| = 3 vibration-rotation transitions have been observed in the ν₄ band of ¹⁵NH₃. The analysis of these transitions, together with previously published data on the allowed transitions, has made it possible to determine a set of molecular parameters, including for the first time the rotational constant C as well as the centrifugal distortion constants D_K and H_KKK, which are necessary for the calculation of energy levels. Some weak forbidden transitions in the ν₂ band have also been observed.     

Study of the spectrum of the Kr-CO weakly bound molecular complex in the millimeter-wavelength range

The rotational spectrum of the weakly bound Kr-CO molecular complex formed in a pulsed molecular jet has been measured in the frequency range 112?C150 GHz on an intracavity orotron-based spectrometer. The measured b-type transitions include the R branch of the band K = 1-0 with the rotational numbers J from 16 to 25 and the P branch of the band K = 2-1 with the rotational numbers J from 13 to 17. For the K = 1-0 band, we succeeded in recording transitions in complexes that consist of all stable Kr isotopes, i.e., ⁸⁴Kr-CO, ⁸⁶Kr-CO, ⁸²Kr-CO, ⁸³Kr-CO, and ⁸⁰Kr-CO. For the K = 2-1 band, we observed transitions in the two most abundant isotopologues, ⁸⁴Kr-CO and ⁸⁶Kr-CO. The obtained data were used to determine the rotational and centrifugal constants of the Kr-CO complex.     

Nuclear levels in228Th populated in the decay of228Pa

The electron-capture decay of²²⁸Pa to levels in²²⁸Th has been studied using mass-separated sources and high-resolutionγ-ray and conversion-electron spectroscopy. A level at 979.5 keV is assigned as 2⁺ member of a second excited K_π=0⁺ band, with the 0⁺ band head at 938.6 keV. The 2⁺ and 3⁺ members of a second excited K_π=2⁺ band at 1153.5 and 1200.5 keV, which decay by strongE0 transitions to the 969 keVγ-vibrational band, are confirmed. In addition we tentatively propose a K_π=1⁺ band at 944 keV. The K_π=0^?, 1^? and 2^? members of the octupole quadruplet are confirmed, and theγ decay of these levels is analysed in an approach, in which the mixing of the octupole bands by the Coriolis interaction is taken into account. It is suggested that octupole correlations might be important for theE1 transition moments. A total of 29 levels is observed between ～1.4 and ～2.0 MeV, for which the nuclear structure, and the possible assignment to rotational bands, is unclear.     

Resonance conversion of gamma radiation in the radiative transitions between neutron resonances

The influence of the resonance conversion on the α-particle spectra in the reaction (n, α) in low-energy transitions between neutron resonances is discussed. Unusual α spectra from neutron resonances in the reaction ¹⁴⁷Sm(n, α)¹⁴⁴Nd are considered as an example of such influence. The calculation of resonance conversion coefficients was performed for the transitions from K shell in the free levels of P shell of Sm atom. The large effect of resonance in the radiative transitions for the nuclei and atomic electron shells is observed.     

Seven and nine quasi-particleK-isomers in175Hf

NewK-isomers with very high spin (up to 57/2) have been found in¹⁷⁵Hf. This is the highest spin isomer seen in deformed nuclei and involves 9 quasi-particles. The predominant decay to the I=55/2 state in aK ^π=35/2^?, 5 quasi-particle rotational band further demonstrates the surprising breakdown of theK-selection rules, reported previously in neighbouring nuclei.     

NMR multiple-quantum processes in a doubly rotating frame in solids

Multiple-quantum transitions between nuclear spin Zeeman levels of fluorine nuclei in a CaF₂ single crystal are studied by a rotary-saturation method in NMR. The theoretical studies are performed for the system consisting of spins interacting with each other through dipole-dipole coupling. The analysis of the behavior of nuclear magnetization, the second quantization of a perturbing field, and the calculation of the nth-order timedependent perturbation are all performed in the reference frame of a doubly rotating system. We found evidence that (1) one type of single spin-n quantum transitions is taking place, but another type of two spin-n quantum transitions is not confirmed yet in this crystal; (2) the linewidths of the multiple-quantum absorptions are extremely narrow at the magic angle but do not completely vanish because of the presence of a perturbing field; (3) the effects of the energy level mixing through the dipole-dipole interactions on the multiple-quantum transitions are negligible over a wide range around the magic angle; and (4) the inhomogeneity of the RF field used to quantize the spin system in the rotating frame affects considerably the results of the rotary-saturation experiments.     

Partial level density of n-quasiparticle excitations, radiative strength functions and new experimental information on the dynamics of nuclear structure change in the B n range

The most reliable at present values of the level density in the fixed spin window and the sums of radiative strength functions of cascade gamma transitions are obtained from analysis of intensities of two-step cascades excited upon thermal neutron capture for approximately 40 nuclei in the mass range 40 ≤ A ≤ 200. The maximal reliability of these data is provided by the experimental conditions—minimum possible propagation error coefficients and practically unique solution of the problem of determination of gamma decay parameters from measured spectra. The experimental data are approximated by the sum of partial level densities corresponding to excitation of n quasiparticles. Steplike structures in the level density at excitation energies smaller than 3–4 MeV are described with good accuracy as the superposition of two-quasiparticle (three-quasiparticle in odd A nuclei) and vibrational excitations with the coefficient of collective density enhancement K _coll ≈ 10?20. They correspond to excitation-energy-correlated maximum enhancement of the radiative strength functions of primary gamma transitions. The level density at larger excitation energies is well reproduced if the breakup of at least two more Cooper pairs of nucleons is taken into account. The increase in the number of excited quasiparticles in the nucleus corresponds to unconditional reduction of the radiative strength functions of primary gamma transitions of the compound state decay. However, the maximum possible value of partial widths of primary transitions increases regularly with decreasing energy. Some ambiguity in the results of approximation and divergence from existing theoretical ideas of the energy dependence of nucleon correlation functions in an excited nucleus point to the possibility of direct extraction from experiment of fundamentally new information on the structure of excited nuclear levels in the range of the neutron binding energy. These are, first of all, the parameters of dependence of nucleon correlation functions on the excitation energy of the nucleus.     

Excited states of 176Hf

The properties of the excited levels of the even-even deformed nucleus ¹⁷⁶Hf are analyzed on the basis of available experimental data on ¹⁷⁶Ta decay. Thirty-nine new states are included in the energy-level scheme of the ¹⁷⁶Hf nucleus. The deexcitation of a number of known levels is supplemented with new transitions. New levels are included in three rotational bands, and the K _i =0 ₄ ⁺ band is identified. The 2470.95-keV level is considered as a two-phonon quadrupole-octupole state. A strong interplay of states belonging to different bands is indicated. The Coriolis interaction is calculated for pairs of K ^π = 0^? and 1^?, 0⁺ and 2⁺, and 2⁺ and 3⁺ bands. The interaction parameters are found. It is shown that the sets of positive-and negative-parity states are connected by El transitions characterized by large hindrance factors.     

Laser magnetic resonance spectra of NH2 in the 9-μm region: Observation of weak ΔKa = −3 transitions in the ν2 band

Laser magnetic resonance spectra of the ν₂ band of the NH₂ radical have been observed with a CO₂ laser in the 1030–1108-cm^?1 range. The measurements of these weak ΔN = ?1, ΔK_a = ?3 transitions, involving levels with 5 ≤ N ≤ 10, should complement measurements in the higher frequency half of the band (1500–1900 cm^?1) made using CO lasers.     

Inversion of the Ka = 0 and 1 rotational levels in the lowest excited vibrational state of HNCS

Fairly strong, regularly spaced absorption lines have been observed in the microwave spectrum of HNCS and assigned to b-type, K_a = 0 ← 1, Q-branch transitions arising from molecules in the lowest excited vibrational state. The Fortrat diagram of these lines has the appearance of a c-type Q branch, which is impossible in HNCS because of its symmetry. This anomalous b-type Q-branch spectrum is caused by strong a-type Coriolis interactions among the three low-lying bending modes; the K_a = 1 levels of the lowest excited vibrational state are perturbed and shifted lower in energy than the K_a = 0 levels for each J. This interpretation has been confirmed by the observation of P- and R-branch transitions associated with this Q branch. The band origin has been determined to be ?40 104.287 MHz (?1.3377 cm^?1). The inversion of the K_a = 0 and 1 energy levels is consistent with the interpretation of HNCS as a quasi-linear molecule.     

Determination of absoluteK-internal conversion coefficients of some transitions in Ce140 by the internal-external conversion method

The internalK-conversion coefficients of the 331, 431, 815 and 933 keV transitions following the decay of La¹⁴⁰ have been determined absolutely by the method of comparing internal and external conversion lines measured in a double — focusing beta — ray spectrometers. TheK-internal conversion coefficients of the 4+→2+ 487 keV transition in Ce¹⁴⁰ was used to normalize relativeK-electron and gamma-ray intensities for these transitions. The results obtained are:α _K (331)=0.04432±0.00471,α _K (431)=0.28110±0.02913,α _K (815)=0.00396±0.00043,α _K (933)=0.00282±0.00031. Multipolarity assignments based on these values are suggested. The 815 keV transition is found to be pure magnetic dipole character in good agreement with the theoretical values calculated bySliv andBand. The 331 and 933 keV transitions are proved to have magnetic dipole character withE2/M1 equal 0.2852±0.0143 and 0.1750±0.0088 respectively. The 431 keV transition was found to have magnetic octupole character. The results obtained are most consistent with the assignment 2+, 4+, 2+, 3+ and 1+ for the 1597, 2084, 2184, 2410 and 2515 keV levels respectively.     

Studying the low-energy region of the 177m Lu gamma spectrum

High-precision measurements of the relative intensities of KX- and γ-rays associated with the decay of the isomer state in ¹⁷⁷Lu (T _1/2 = 160.44 days) are performed using a γ spectrometer that incorporates four different types of semiconductor detectors. Detailed analysis of the balance of intensities of the excited levels in ¹⁷⁷Lu and ¹⁷⁷Hf confirms the consistency of the obtained data. The intensities of the γ- and β—decay branches of the isomer and the internal conversion coefficients of the K-forbidden transitions are determined.     

Level structure of217Rn and221Ra investigated in the alpha-decay225Th →221Ra →217Rn

The nuclei²²¹Ra and²¹⁷Rn have been investigated in the α-decay chain²²⁵Th→²²¹Ra →²¹⁷Rn through γ-ray and conversion-electron studies. The short-lived²²⁵Th nuclei (T _1/2=8min) were produced in the²²⁶Ra(α, 5n) reaction, and γ-rays and conversion electrons were measured — between the irradiation periods — in coincidence with αparticles. In²²¹Ra the five lowest levels are interpreted as members of aK=5/2 paritydoublet with ΔE_π=104 keV. These levels, as well as a higher-lying K^π=3/2⁺ band, are consistent with an octupole deformation of²²¹Ra, as expected from theoretical considerations. In²¹⁷Rn only three excited levels are observed, with a favoured α-decay to a 5/2⁺ excited level thus establishing positive parity for the ground state of²²¹Ra.     

Rotations and intrinsic Kπ = 1+ excitations in deformed rare-earth nuclei

The K^π = 1⁺ intrinsic excitations in deformed rare-earth nuclei are studied in the framework of the random-phase approximation, which excludes the spurious state (zero-energy excitation) related with the rotation of the whole nucleus. We take the Nilsson-plus-pairing, quadrupole and spin-dependent (magnetic dipole or spin-quadrupole) force model. Cranking-model formulae for the moment of inertia and the collective gyromagnetic ratio are derived as the zero-energy limit of the lowest K^π = 1⁺ excitation. They are modified from the usual formulae due to the spin-dependent force. The M1 and E2 transitions from the K^π = 1⁺ excited states to the ground state of ¹⁷⁰Yb are also calculated. The M1 transition strengths are concentrated almost below 6 MeV, while the E2 ones are scattered even up to 12 MeV. Several levels around 12 MeV show rather strong E2 transitions of ΔN = 2 character.     

The fundamental band ν2 of D2CO

The ν₂ band of D₂¹³CO in the region of 1570-1760 cm⁻¹ has been analyzed with high accuracy. The limits of the quantum numbers J and K_a are 50 and 16, respectively. The number of the assigned transitions is 3858. A local anharmonic resonance ν₂/2ν₄ at K_a =  8-12 was observed. The Watson’s A-reduced Hamiltonian and anharmonic resonance term were fitted to the observed transitions. The fit resulted in the band center and rotational parameters of the ν₂ band as well as the effective parameters for the 2ν₄ band and anharmonic resonance parameter. The rms deviation of the transitions in the ν₂ band was 0.000364 cm⁻¹.