Photolysis of NO2 at multiple wavelengths in the spectral region 200–205 nm

A study of the photodissociation dynamics of NO₂ in the 200–205 nm region using resonance enhanced multiphoton ionization (REMPI) in conjunction with the velocity map imaging technique is presented. We chose this region because it allowed the use of a single laser to photodissociate the NO₂ molecule and probe both the O(¹D₂) fragment using (2+1) REMPI via the 3p'¹P₁ state at 2 ×205.47 nm and the 3p'¹F₃ state at 2 ×203.5 nm, and the O(³P_J) fragments using (2+1) REMPI via the P_J states around 2 ×∼200 nm. Translational energy and angular distributions are extracted from the O(¹D) and O(³P) product images. A growth in the population of highly excited vibrational levels of the NO X(²Π) co-fragment is found as the dissociation wavelength decreases. These are compared with similar trends observed previously for other triatomic O-atom containing molecules. Detailed information on the electronic angular momentum alignment of the ¹D₂ state is obtained from analysis of the polarization sensitivity of the O(¹D) images using the two resonant intermediate states. The angular dependence of the potential energy in the exit channels is examined using long-range quadrupole-dipole and quadrupole-quadrupole interaction terms, from which molecular-frame multipole moments of the total angular momentum of the recoiling O atoms have been calculated. Comparison with the experimentally derived multipole moments is used to help provide insight into the dissociation mechanism.     

Resonance enhanced multi-photon ionization of neutral atoms sputtered with Ga-FIB

Resonance enhanced multi-photon ionization (REMPI) of neutral aluminum atoms sputtered with gallium focused ion beam (Ga-FIB) was studied in terms of substrate temperature and chemical state of the surfaces. Aluminum has the lowest excitation state (3p ²P_3/2) at 112 cm⁻¹ above the ground state (3p ²P_1/2). The results showed that the total REMPI signal intensity of neutral aluminum atoms and the ratio of REMPI signal intensities attributed to ²P_1/2 to ²P_3/2 were increased at higher temperature. On the other hand, the REMPI signal and the ratio were decreased in the case of partially oxidized aluminum surfaces. Considering the result on Al₂O₃, it was confirmed that the REMPI signals of ground state ²P_1/2 and the first excited spate ²P_1/2 could be affected with surface oxidation state.     

Momentum dependence of pseudogap and superconducting gap in variation theory

To consider the origin of a pseudogap and a superconducting (SC) gap found in the high-T_c cuprates, we evaluated the momentum dependence of the singlet gap corresponding to the pseudogap and the SC gap in the t–J model, using an optimization variational Monte Carlo (VMC) method. In the underdoped regime, the singlet gap is significantly modified from the simple d_x²-y²(d)-wave gap (∝ cos k_x − cos k_y) by the contribution of long-range pairings. Its angular dependence at the quasi Fermi surface is qualitatively consistent with those experimentally observed in both hole and electron-doped cuprates. On the other hand, a SC gap is almost unchanged, preserving the original simple d-wave form. Thus, it seems that the incoherent part of the singlet gap mainly influences the forms of observed gaps.     

The Fe(α, γ)Ni reaction at excitation energies in the region of the giant dipole resonance

Excitation functions for the ⁵⁶Fe(α, γ₀)⁶⁰Ni and ⁵⁶Fe(α, γ₁)⁶⁰Ni reactions have been measured at 90° to the beam direction over the bombarding energy range 8.0–17.6 MeV. Gamma-ray angular distributions were measured at ten bombarding energies. Excitation functions for the ⁵⁹Co(p, γ₀)⁶⁰Ni and ⁵⁹Co(p, γ₁)⁶⁰Ni reactions were measured over the range E_x = 16.58–16.92 MeV and compared with the (α, γ) data. The angular distribution data indicate that the (α, γ₀) and (α,γ₁) reactions proceed through 1⁻, and 1⁻ and 3⁻ states, respectively. The (α, γ) excitation functions are discussed with respect to isospin splitting of the ⁶⁰Ni giant dipole resonance. The fine structure observed in the excitation functions is shown to be most probably due to Ericson fluctuations. The gross (α, γ) cross sections are shown to be in reasonable agreement with the results of calculations made using the theory of Hauser and Feshbach assuming excitation of the giant dipole resonance.     

Gamma-ray spectroscopy of Cr

A study of low-lying states in the self-conjugate nucleus ⁴⁸Cr has been performed with the reaction ⁴⁰Ca(¹⁰B, pnγ)⁴⁸Cr. Several techniques of γ-ray spectroscopy have been used: activity measurements, γ-ray angular distributions, γ-γ coincidences, p-n-γ triple coincidences, and recoil-distance lifetime measurements. The following level energies, spin-parity assignments, and lifetimes have been found: 752.4±0.5 keV, 2₁⁺, τ_m = 9.7±2.6 ps; 1858.7±0.7 keV, 4₁⁺, τ_m = 1.5_−0.5^+2.0 ps; 3532.7±1.2 keV, (6₁⁺); 4064.3±1.3 keV, ( 4), τ_m < 60 ps. The 2₁⁺ state in ⁴⁸Cr is found to have the lowest excitation energy and highest E2 transition strength (33±9 W.u.) among the 2₁⁺ states of even nuclei in the 1f shell.     

Analysis of autoionizing Rydberg states in the vacuum ultraviolet absorption spectrum of HBr and DBr

The photographic absorption spectrum of HBr and DBr above the first ionization limit (800–1000 Å) has been analyzed. No analyzable rotational structure was observed, indicating that the autoionization rate is faster than the rotational period. Two Rydberg series converging to the second ionization limit (²Σ⁺) have been identified, one with n^* = 2.75, 3.74, ,14.7, and the other with n^* = 2.35, 3.38. The symmetries cannot be determined conclusively, but the most probable assignment for the first series is 4pσ 4pπ⁴nsσ (¹Σ⁺) N = 6, 7, , 18, and for the second, 4pσ 4pπ·npσ and/or npπ[¹Σ⁺, ¹Π] N = 5, 6. Assuming that the intensity maxima assigned are band origins of vibronic states, a new ionization limit can be determined for HBr⁺(²Σ⁺): T₀ = 123 373 ± 20 cm⁻¹.     

On integrability of generalized Veronese curves of distributions

Given a 1-parameter family of 1-forms γ(t) = γ₀+tγ₁+ ···+tⁿψ_n, consider the condition dγ(t)γ(t) = 0 (of integrability for the annihilated by γ(t) distribution w(t)). We prove that in order that this condition is satisfied for any t it is sufficient that it is satisfied for N = n + 3 different values of t (the corresponding implication for N = 2n + 1 is obvious). In fact we give a stronger result dealing with distributions of higher codimension. This result is related to the so-called Veronese webs and can be applied in the theory of bihamiltonian structures.     

(2 + 1) Resonance enhanced multiphoton ionization of hydrogen chloride in a pulsed supersonic jet: Vacuum wavenumbers of rotational lines with detailed band analysis for excited electronic states of HCl

A comprehensive study of the excited electronic states of HCl is reported. Using resonance enhanced multiphoton ionization ((2 + 1) REMPI) and time-of-flight mass spectrometry (TOFMS) over 120 band systems are analyzed. Supersonic jet techniques are used to prepare rotationally cold species for laser spectroscopy in the 77 000 to 96 000 cm⁻¹ region. At least 50 new electronic states are characterized as well as several features only tentatively assigned previously. A long vibrational progression consisting of 29 vibrational levels of the deeply bound V¹Σ⁺(0⁺) valence/ion-pair state is studied. We also extend the identification and analysis to high vibrational levels of low-lying Rydberg states. The assignments of [²Π_i] Rydberg state complexes are evaluated in terms of spin-orbit coupling and united-atom calculations. In several band systems, the spectra exhibit anomalous rotational line intensities and broadened linewidths which are consistent with predissociation. Multiphoton ionization with mass spectrometry permits the investigation of isotope effects as well as the appearance of fragment species associated with repulsive potential curves.     

Interaction of oxovanadium(IV) with carboxylic ligands in aqueous solution: A thermodynamic and visible spectrophotometric study

The hydrolysis of VO²⁺ and the complex with sulfate were studied potentiometrically, spectrophotometrically and calorimetrically, in NaCl aqueous solution (0 < I ≤ 1 mol L^− 1) and at t = 25 °C. The formation of two hydrolytic species VO(OH)⁺ and VO₂(OH)₂²⁺ and one complex with sulfate was found, with log β = − 5.65 for the reaction VO²⁺ + H₂O = VO(OH)⁺ + H⁺, log β = − 7.02 for the reaction 2VO²⁺ + 2H₂O = (VO)₂(OH)₂²⁺ + 2H⁺ and log K = 1.73 for VOSO₄⁰ species (at I = 0.1 mol L^− 1 and t = 25 °C). For these species, using calorimetric data, ΔH and TΔS values were also obtained. By using the above values, interactions of VO²⁺ with acetate (ac), malonate (mal), succinate (suc), 1,2,3-propanetricarboxylate (tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands were studied potentiometrically and spectrophotometrically. The formation of ML⁺, ML₂⁰ and MLOH⁰ for ac; ML⁰, MLH⁺, ML₂²⁻ and ML₂H⁻ for mal; ML⁰, MLH⁺ and MLOH⁻ for suc; ML⁻ and MLH⁰ for tca and ML²⁻, MLH⁻ and MLH₂⁰ for btc were found. Formation constants are reported at I = 0.1 mol L^− 1, together with SIT parameters for the dependence on ionic strength. By visible spectrophotometric measurements, λ_max and ε_max values for the relevant species in solution were determined.     

离子速度成像系统校准及1,4-氯溴丁烷的紫外光解动力学

大气臭氧层破坏越来越严重, 卤代烷烃在太阳紫外线辐射下解离生成破坏臭氧的游离态卤素原子, 是主要元凶之一. 本文选用碘甲烷作为校准分子, 利用离子速度成像技术和共振增强多光子电离技术测得碘甲烷在266 nm紫外光解离下产生的基态碘原子I(²P_3/2)在不同聚焦电压下的离子速度影像, 得到离子速度成像系统的放大系数N=1.13. 并利用该系统研究了1, 4-氯溴丁烷在～ 234 nm紫外辐射下的解离动力学, 分析讨论了解离产生的基态Br (²P_3/2)和激发态Br^* (²P_1/2)的速度和角度分布信息, 揭示了1, 4-氯溴丁烷在～ 234 nm紫外光解离产生基态Br原子和激发态Br^* 原子的通道都是源于C-Br键排斥势能面上的快速解离. 文中通过计算碎片影像角度分布的各项异性参数β值, 得到了生成基态Br(²P_3/2)和激发态Br^* (²P_1/2) 两个解离通道中的平行跃迁和垂直跃迁比例. 另外, 本文还对氯溴甲烷, 1, 2-氯溴乙烷, 1, 3-氯溴丙烷和1, 4-氯溴丁烷在～ 234 nm下的光解动力学进行比较, 分析得到双卤代烷烃分子解离机理对烷基支链长度的依赖关系.     

A combined ab initio, Fourier transform microwave and Fourier transform infrared spectroscopic investigation of β-propiolactone: The ν8 and ν12 bands

The pure rotational spectrum of β-propiolactone (c-C₂H₄COO) has been recorded between 7 and 21 GHz using a pulsed jet Fourier transform microwave spectrometer. The resulting ground state spectroscopic constants guided the analysis of the rotationally-resolved infrared spectra of two bands that were collected using the far infrared beamline at the Canadian Light Source synchrotron. The observed modes correspond to motions best described as ring deformation (ν₁₂) at 747.2 cm⁻¹ and CO ring stretching (ν₈) at 1095.4 cm⁻¹. A global fit of 4430 a- and b-type transitions from the microwave spectrum and the two infrared bands provided an accurate set of ground state and excited state spectroscopic parameters. To complement the experimental results, the harmonic and anharmonic vibrational frequencies of all 21 infrared active modes of β-propiolactone have been calculated using the DFT B3LYP method (6-311+G(d,p), 6-311++G(2d,3p) basis sets).     

Polarization spectroscopy of ion-pair states of ICl

Molecular constants for the E0⁺(³P₂) and 1(³P₂) ion-pair states of ICl vapor have been determined using sequential two-photon polarization-labeling spectroscopy. The two states are coupled by a heterogeneous perturbation which is analyzed in some detail for low-lying vibrational levels of 1(³P₂). The I³⁵Cl potential constants for the 1(³P₂) state and the rotation-vibration constants for the set of f sublevels—i.e., the constants unaffected by coupling with the E state—are (in cm⁻¹) 1(³P₂): Y_0,0= 39103.814(32), Y_1,0= 170.213(15), Y_2,0= −0.4528(22), Y_3,0= −7.0(12) × 10⁻⁴, Y_4,0= −1.48(24) × 10⁻⁵ and Y_5,0= −6.6(19) × 10⁻⁸, Y^(f)_0,1= 5.6878(17) × 10⁻² Y^(f)_1,1= −2.110(24) × 10⁻⁴, Y^(f)_2,1= −1.23(62) × 10⁻⁷, and Y^(f)_0,1= −3.08(22) × 10⁻⁸Likewise, the I³⁵Cl constants determined for the E 0⁺(³P₂) state are E 0⁺(³P₂: Y_0,0= 39054.38(61), Y_1,0= 166.96(10), Y_2,0 = −0.3995(42), Y_0,1= 5.738(31) × 10⁻², and Y_1,1= −1.67(26) × 10⁻⁴Practical constraints in pumping the sequence E 0⁺ ← B 0⁺ ← × 0⁺ restrict the analysis of the E state to levels v = 9–15. Given the long extrapolation to the equilibrium state the 3σ statistical uncertainties quoted for these constants should be treated with caution.     

Two-step excitation of an auto-ionized state of the Ba atom associated with two-photon excitation of an intermediate state

An experimental and theoretical study is performed of the angular photoelectron distribution for three-photon ionization of Ba atoms through the 2ω-excited intermediate state 6p ²(¹ S ₀) and the auto-ionized state 6p8s(³ P ₁). Rotation of the polarization plane of dye-laser radiation allowed us to investigate the photoelectron angular distribution. Electrons were counted with the help of a time-of-flight electron spectrometer. The density-matrix formalism is used to obtain expressions for the angular dependence of the differential ionization probability. Possible experiments are discussed. Zh. éksp. Teor. Fiz. 113, 834–840 (March 1998)     

Looking for double beta decay of Nd to excited states of Sm by gamma ray spectroscopy

We have measured the gamma ray activity of a sample of 6189 grams of metallic Neodimium with a germanium detector. From the gamma energy spectrum recorded during almost 6500 hours we extract lower limits for the halflife of the inclusive (0ν + 2ν) ββ decay of ¹⁵⁰Nd to the first excited states of ¹⁵⁰Sm : t_1/2(0⁺ → 0₁⁺ > 1.0·10²⁰, t_1/2(O⁺ → 0₂⁺) > 2.0 · 10²⁾, t_1/2(0⁺ → 2₁⁺) > 9.1 · 10¹⁹.     

Determination of the (Na) Sternheimer antishielding factor by Na NMR spectroscopy on sodium oxide chloride, Na3OCl

The (Na⁺) Sternheimer antishielding factor γ_∞ (Na⁺) was determined by ²³Na NMR spectroscopy on sodium oxide chloride, Na₃OCl. The quadrupolar coupling constant of the sodium ion in Na₃OCl was determined to QCC=11.34 MHz, which presents the largest coupling constant of a sodium nucleus observed so far. Applying a simple point charge model, the largest principal value of the electric field gradient at the sodium site was calculated to V_zz=−6.76762·10²⁰ V/m². From these values we calculated the (Na⁺) Sternheimer antishielding factor to γ_∞ (Na⁺)=−5.36. In sodium oxide, Na₂O, we observed an isotropic chemical shift of δ_CS=55.1 ppm, referenced to 1 M aqueous NaCl (δ=0 ppm).     

Multiphoton ionization of iodine atoms and CF<Subscript> 3</Subscript>I molecules by XeCl laser radiation

We report about effective ionization of iodine atoms and CF₃I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF₃I molecules is the I⁺ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(²P_3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I^*(²P_1/2). The ionization of the CF₃I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.     

Observation of χb production in the exclusive reaction ′→γγχb→γγ→γγ(eeorμμ−)

We report on the observation of 1 ³P_J (χ_b) production in the reaction ′→γχ_b→γγ→γγ(e⁺e⁻ or μ⁺μ⁻). The data were recorded with the nonmagnetic CUSB detector at the Cornell Electron Storage Ring, CESR. We observe 124 γγ events with either an electron or muon pair in the final state. In the γγ correlation plot about 40% of the events cluster around (120, 430) MeV.     

Density, viscosity, and excess properties of the binary mixture of diethylene glycol monomethyl ether + water at T = (293.15, 303.15, 313.15, 323.15, 333.15) K under atmospheric pressure

Densities and viscosities have been measured as a function of composition for the binary liquid mixture of diethylene glycol monomethyl ether CH₃O(CH₂)₂O(CH₂)₂OH + water at T = (293.15, 303.15, 313.15, 323.15, 333.15) K under atmospheric pressure. Densities were determined using a capillary pycnometer. Viscosities were measured with Ubbelohde capillary viscometer. From the experimental data, the excess molar volumes V^E, and viscosity deviations δη, and the excess energies of activation for viscous flow ΔG^*E were calculated. These data have been correlated by the Redlich–Kister type equations to obtain their coefficients and standard deviations. The results suggest that molecular interaction between diethylene glycol monomethyl ether and water is strong.