Transition probabilities and average cross sections for the Na2 B1pi(u) --> X1sigma(g)+ system using as excitation the 4880 A Ar+ laser line

The fluorescence spectrum of Na2 induced by the 4879.86 A line of an Argon ion laser has been analyzed with special emphasis on determination of accurate relative intensities. We have observed nineteen fluorescence series for the B1pi(u) --> X1sigma(g)+ band system. Some series are reported for the first time. The radiative transition probabilities for the observed fluorescence series were calculated using hybrid potential energy curves for the B1pi(u) and X1sigma(g)+ states constructed up to dissociation and a B-X transition dipole moment function. Radiative lifetimes for the rovibrational levels of the upper states pumped by the laser line have also been calculated. The transition probabilities and lifetimes agree with the corresponding observed measurements usually within the experimental uncertainty. From the rotational satellite structure with deltaJ' = +/- 1, +/- 2...+/- 20, for some nu'-bands of the most intense fluorescence series induced by emission from the vibrational-rotational levels: nu' = 6, J' = 43 and v' = 9, J' = 56, collision-induced transition rates and average cross sections have been obtained.     

Measurement of the electronic transition dipole moment by Autler-Townes splitting: Comparison of three- and four-level excitation schemes for the Na2 A 1Sigma(u)+ - X 1Sigma(g)+ system

We present a fundamentally new approach for measuring the transition dipole moment of molecular transitions, which combines the benefits of quantum interference effects, such as the Autler-Townes splitting, with the familiar R-centroid approximation. This method is superior to other experimental methods for determining the absolute value of the R-dependent electronic transition dipole moment function mu(e)(R), since it requires only an accurate measurement of the coupling laser electric field amplitude and the determination of the Rabi frequency from an Autler-Townes split fluorescence spectral line. We illustrate this method by measuring the transition dipole moment matrix element for the Na2 A 1Sigma(u)+ (v' = 25, J' = 20e)-X 1Sigma(g)+ (v" = 38, J" = 21e) rovibronic transition and compare our experimental results with our ab initio calculations. We have compared the three-level (cascade) and four-level (extended Lambda) excitation schemes and found that the latter is preferable in this case for two reasons. First, this excitation scheme takes advantage of the fact that the coupling field lower level is outside the thermal population range. As a result vibrational levels with larger wave function amplitudes at the outer turning point of vibration lead to larger transition dipole moment matrix elements and Rabi frequencies than those accessible from the equilibrium internuclear distance of the thermal population distribution. Second, the coupling laser can be "tuned" to different rovibronic transitions in order to determine the internuclear distance dependence of the electronic transition dipole moment function in the region of the R-centroid of each coupling laser transition. Thus the internuclear distance dependence of the transition moment function mu(e)(R) can be determined at several very different values of the R centroid. The measured transition dipole moment matrix element for the Na2 A 1Sigma(u)+ (v' = 25, J' = 20e)-X 1Sigma(g)+ (v" = 38, J" = 21e) transition is 5.5+/-0.2 D compared to our ab initio value of 5.9 D. By using the R-centroid approximation for this transition the corresponding experimental electronic transition dipole moment is 9.72 D at Rc = 4.81 A, in good agreement with our ab initio value of 10.55 D.     

Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: two-dimensional resonance enhanced multiphoton ionization of HBr via singlet-, triplet-, Ω = 0 and 2 states

Mass spectra were recorded for one-colour resonance enhanced multiphoton ionization (REMPI) of H(i)Br (i = 79, 81) for the two-photon resonance excitation region 79,040-80,300 cm(-1) to obtain two-dimensional REMPI data. The data were analysed in terms of rotational line positions, intensities, and line-widths. Quantitative analysis of the data relevant to near-resonance interactions between the F(1)Δ(2)(v' = 1) and V(1)Σ(+)(v' = m + 7) states gives interaction strengths, fractional state mixing, and parameters relevant to dissociation of the F state. Qualitative analysis further reveals the nature of state interactions between ion-pair states and the E(1)Σ(+) (v' = 1) and H(1)Σ(+)(v' = 0) Rydberg states in terms of relative strengths and J' dependences. Large variety in line-widths, depending on electronic states and J' quantum numbers, is indicative of number of different predissociation channels. The relationship between line-widths, line-shifts, and signal intensities reveals dissociation mechanisms involving ion-pair to Rydberg state interactions prior to direct or indirect predissociations of Rydberg states. Quantum interference effects are found to be important. Moreover, observed bromine atom (2 + 1) REMPI signals support the importance of Rydberg state predissociation channels. A band system, not previously observed in REMPI, was observed and assigned to the k(3)Π(0)(v' = 0) ←← X transition with band origin 80,038 cm(-1) and rotational parameter B(v('))=7.238 cm(-1).     

Oscillator strengths and line widths of dipole-allowed transitions in (14)N(2) between 89.7 and 93.5 nm

Line oscillator strengths in the 20 electric dipole-allowed bands of (14)N(2) in the 89.7-93.5 nm (111480-106950 cm(-1)) region are reported from photoabsorption measurements at an instrumental resolution of approximately 6 mA (0.7 cm(-1)) full width at half maximum. The absorption spectrum comprises transitions to vibrational levels of the 3p sigma(u) c(4)' (1)Sigma(u)(+), 3p pi(u) c(3) (1)Pi(u), and 3s sigma(g) o(3) (1)Pi(u) Rydberg states and of the b' (1)Sigma(u)(+) and b (1)Pi(u) valence states. The J dependences of band f values derived from the experimental line f values are reported as polynomials in J'(J'+1) and are extrapolated to J'=0 in order to facilitate comparisons with results of coupled Schrodinger-equation calculations. Most bands in this study are characterized by a strong J dependence of the band f values and display anomalous P-, Q-, and R-branch intensity patterns. Predissociation line widths, which are reported for 11 bands, also exhibit strong J dependences. The f value and line width patterns can inform current efforts to develop comprehensive spectroscopic models that incorporate rotational effects and predissociation mechanisms, and they are critical for the construction of realistic atmospheric radiative-transfer models.     

Oscillator strength and linewidth measurements of dipole-allowed transitions in 14N2 between 93.5 and 99.5 nm

Line oscillator strengths in 16 electric dipole-allowed bands of 14N2 in the 93.5-99.5 nm (106,950-100,500 cm(-1)) region have been measured at an instrumental resolution of 6.5 x 10(-4) nm (0.7 cm(-1)). The transitions terminate on vibrational levels of the 3psigma 1Sigma u (+), 3ppi 1Pi u, and 3ssigma 1Pi u Rydberg states and of the b' 1Sigma u (+) and b 1Pi u valence states. The J dependences of band f values derived from the experimental line f values are reported as polynomials in J'(J'+1) and are extrapolated to J'=0 in order to facilitate comparisons with results of coupled-Schrodinger-equation calculations that do not take into account rotational interactions. Most bands in this study reveal a marked J dependence of the f values and/or display anomalous P-, Q- and R-branch intensity patterns. These patterns should help inform future spectroscopic models that incorporate rotational effects, and these are critical for the construction of realistic atmospheric radiative transfer models. Linewidth measurements are reported for four bands. Information provided by the J dependences of the experimental linewidths should be of use in the development of a more complete understanding of the predissociation mechanisms in N2.     

The dissociation dynamics of He...I 35Cl(B,v'=2,3) complexes with varying amounts of internal energy

The He...I (35)Cl intermolecular vibrational levels with n'=0-6 that are bound within the He+ICl(B,v'=3) potential [A. B. McCoy, J. P. Darr, D. S. Boucher, P. R. Winter, M. D. Bradke, and R. A. Loomis, J. Chem. Phys. 120, 2677 (2004)] are identified in laser-induced fluorescence experiments performed at very low temperatures within a supersonic expansion. Comparisons of the positions and intensities of these lines with the excitation spectra, calculated using potential surfaces to describe the interactions between the helium atom and ICl in its ground and excited state, assist in the assignments. Based on these comparisons the excited state potential was rescaled so that the experimental and calculated J'=0 energies agree to within the experimental uncertainties for all but the lowest, n'=0, intermolecular level. Two-laser, action, and pump-probe spectroscopy experiments indicate that the bound He...I (35)Cl(B,v'=3) intermolecular vibrational levels undergo vibrational predissociation forming rotationally excited I (35)Cl(B,v'=2,j') products with distributions that depend upon the initial intermolecular vibrational level excited. Action spectra recorded in the ICl B-X, 2-0 region while monitoring the Deltav=0, I (35)Cl(B,v'=2) channel reveal two additional dissociation mechanisms for the He...I (35)Cl(B,v') excited state complexes: rotational predissociation of discrete metastable states lying slightly above the He+I (35)Cl(B,v'=2) asymptote and direct dissociation that occurs when the linear conformer is excited to the continuum of states above the same asymptote. The rotational predissociation pathway forms I (35)Cl(B,v'=2,j') products in all of the rotational states energetically accessible. The direct dissociation mechanism yields very cold rotational product state distributions; for instance, the average rotational energy in the product state distribution measured when the linear complexes are prepared 20 cm(-1) above the dissociation limit is only 1.51 cm(-1), representing only 7.6% of the available energy.     

Fourier transform spectroscopy and direct potential fit of a shelflike state: application to E(4)1Σ(+) KCs

The paper presents high-resolution experimental study and a direct potential construction of a shelflike state E(4)(1)Σ(+) of the KCs molecule converging to K(4(2)S) + Cs(5(2)D) atomic limit; such data are of interest for selecting optical paths for producing and monitoring cold polar diatomics. The collisionally enhanced laser induced fluorescence (LIF) spectra corresponding to both spin-allowed E(4)(1)Σ(+) → X(1)(1)Σ(+) and spin-forbidden E(4)(1)Σ(+) → a(1)(3)Σ(+) transitions of KCs were recorded in visible region by Fourier transform spectrometer with resolution of 0.03 cm(-1). Overall about 1650 rovibronic term values of the E(4)(1)Σ(+) state of (39)K(133)Cs and (41)K(133)Cs isotopologues nonuniformly covering the energy range [16987, 18445] cm(-1) above the minimum of the ground X-state were determined with the uncertainty of 0.01 cm(-1). Experimental data field is limited by vibrational levels v' ∈ [2, 74] with rotational quantum numbers J' ∈ [1, 188]. The closed analytical form for potential energy curve (PEC) based on Chebyshev polynomial expansion (CPE) was implemented to a direct potential fit (DPF) of the experimental term values of the most abundant (39)K(133)Cs isotopologue. Besides analyticity, regularity, correct long-range behavior, and nice convergence properties, the CPE form demonstrated optimal balance on flexibility and constraint for the DPF of a shelflike state aggravated by a limited data set. The mass-invariant properties of the CPE PEC were tested by the prediction of rovibronic term values of the (41)K(133)Cs isotopomer which coincided with their experimental counterparts with standard deviation of 0.0048 cm(-1). The CPE modeling is compared with the highly flexible pointwise inverted perturbation approach model, as well as with conventional Dunham analysis of restricted data set v' ≤ 50. Reliability of the empirical PEC is additionally confirmed by good agreement between the calculated and experimental relative intensity distributions in the long E(v') → X(v") LIF progressions.     

Dynamics of N-OH bond dissociation in cyclopentanone and cyclohexanone oxime at 193 nm: laser-induced fluorescence detection of nascent OH (v', J')

Cyclohexanone oxime (CHO) and cyclopentanone oxime (CPO) in the vapor phase undergo N-OH bond scission upon excitation at 193 nm to produce OH, which was detected state selectively employing laser-induced fluorescence. The measured energy distribution between fragments for both oximes suggests that in CHO the OH produced is mostly vibrationally cold, with moderate rotational excitation, whereas in CPO the OH fragment is also formed in v' = 1 (~2%). The rotational population of OH (v' = 0, J') from CHO is characterized by a rotational temperature of 1440 ± 80 K, whereas the rotational populations of OH (v' = 0, J') and OH (v' = 1, J') from CPO are characterized by temperatures of 1360 ± 90 K and 930 ± 170 K, respectively. A high fraction of the available energy is partitioned to the relative translation of the fragments with f(T) values of 0.25 and 0.22 for CHO and CPO, respectively. In the case of CHO, the Λ-doublet states of the nascent OH radical are populated almost equally in lower rotational quantum levels N', with a preference for Π(+) (A') states for higher N'. However, there is no preference for either of the two spin orbit states Π(3/2) and Π(1/2) of OH. The nascent OH product in CPO is equally distributed in both Λ-doublet states of Π(+) (A') and Π(-) (A') for all N', but has a preference for the Π(3/2) spin orbit state. Experimental work in combination with theoretical calculations suggests that both CHO and CPO molecules at 193 nm are excited to the S(2) state, which undergoes nonradiative relaxation to the T(2) state. Subsequently, molecules undergo the N-OH bond dissociation from the T(2) state with an exit barrier to produce OH (v', J').     

Collisional deactivation of Ba 5d7p (3)D1 by noble gases

Collisional deactivation of the 5d7p (3)D1 state of Ba by noble gases is studied by time- and wavelength-resolved fluorescence techniques. A pulsed, frequency-doubled dye laser at 273.9 nm excites the 5d7p (3)D1 level from the ground state, and fluorescence at 364.1 and 366.6 nm from the 5d7p (3)D1 --> 6s5d (3)D1 and 5d7p (3)D1 --> 6s5d (3)D2 transitions, respectively, is monitored in real time to obtain the deactivation rate constants. At 835 K these rate constants are as follows: He, (1.69 +/- 0.08) x 10(-9) cm(3) s(-1); Ne, (3.93 +/- 0.14) x 10(-10) cm(3) s(-1); Ar, (4.53 +/- 0.15) x 10(-10) cm(3) s(-1); Kr, (4.64 +/- 0.13) x 10(-10) cm(3) s(-1); Xe, (5.59 +/- 0.22) x 10(-10) cm(3) s(-1). From time-resolved 5d7p (3)D1 emission in the absence of noble gas and from the intercepts of the quenching plots, the lifetime of this state is determined to be 100 +/- 1 ns. Using time- and wavelength-resolved Ba emission with a low background pressure of noble gas, radiative lifetimes of several near-resonant states are determined from the exponential rise of the fluorescence signals. These results are as follows: 5d6d (3)D3, 28 +/- 3 ns; 5d7p (3)P1, 46 +/- 2 ns; 5d6d (3)G3, 21.5 +/- 0.8 ns; 5d7p (3)F3, 48 +/- 1 ns. Integrated fluorescence signals are used to infer the relative rate constants for population transfer from the 5d7p (3)D1 state to eleven near-resonant fine structure states.     

ESR and optical study of Mn2+-doped sodium hydrogen orthophosphate dihydrate

ESR study of Mn(2+)-doped sodium hydrogen orthophosphate dihydrate (SHOD) single crystals is done at room temperature. The Mn(2+) spin-Hamiltonian parameters have been evaluated employing a large number of resonant line positions observed for different orientations of the external magnetic field. The values of g, A, B, D, E and a are: 2.0042+/-0.0002, 86+/-2 x 10(-4)cm(-1), 83+/-2 x 10(-4)cm(-1), 238+/-2 x 10(-4)cm(-1), 76+/-2 x 10(-4)cm(-1), 13+/-1 x 10(-4)cm(-1) for site I and 2.0032+/-0.0002, 86+/-2 x 10(-4)cm(-1), 83+/-2 x 10(-4)cm(-1), 238+/-2 x 10(-4)cm(-1), 76+/-2 x 10(-4)cm(-1), 13+/-1 x 10(-4)cm(-1) for site II, respectively. The optical absorption study of the crystal is also done. The observed bands are assigned as transitions from the (6)A(1g)(S) ground state to various excited quartet levels of a Mn(2+) ion in a cubic crystalline field. These bands are fitted with four parameters B, C, D(q) and alpha and the values found for the parameters are B=777 cm(-1), C=3073 cm(-1), D(q)=755 cm(-1), and alpha=76 cm(-1). On the basis of the data obtained the surrounding crystalline field and the nature of metal-ligand bonding are discussed.     

Temperature dependence and kinetic isotope effects for the OH + HBr reaction and H/D isotopic variants at low temperatures (53-135 K) measured using a pulsed supersonic Laval nozzle flow reactor

The reactions of OH + HBr and all isotopic variants have been measured in a pulsed supersonic Laval nozzle flow reactor between 53 and 135 K, using a pulsed DC discharge to create the radical species and laser induced fluorescence on the A 2sigma <-- X 2pi (v' = 1 <-- v' = 0) transition. All reactions are found to possess an inverse temperature dependence, in accord with previous work, and are fit to the form k = A(T/298)(-n), with k1 (OH + HBr) = (10.84 +/- 0.31) x 10(-12) (T/298)(-0.67+/-0.02) cm3/s, k2 (OD + HBr) = (6.43 +/- 2.60) x 10(-12) (T/298)(-1.19+/-0.26) cm3/s, k3 (OH + DBr) = (5.89 +/- 1.93) x 10(-12) (T/298)(-0.76+/-0.22) cm3/s, and k4 (OD + DBr) = (4.71 +/- 1.56) x 10(-12) (T/298)(-1.09+/-0.21) cm3/s. A global fit of k vs T over the temperature range 23-360 K, including the new OH + HBr data, yields kT = (1.06 +/- 0.02) x 10(-11) (T/298)(-0.90+/-0.11) cm3/s, and (0.96 +/- 0.02) x 10(-11) (T/298)(-0.90+/-0.03) exp((-2.88+/-1.82 K)/T) cm3/s, in accord with previous fits. In addition, the primary and secondary kinetic isotope effects are found to be independent of temperature within experimental error over the range investigated and take on the value of (kH/kD)(AVG) = 1.64 for the primary effect and (kH/kD)(AVG) = 0.87 for the secondary effect. These results are discussed within the context of current experimental and theoretical work.     

Photophysics of octabutoxy phthalocyaninato-Ni(II) in toluene: ultrafast experiments and DFT/TDDFT studies

Reported herein is a combination of experimental and DFT/TDDFT theoretical investigations of the ground and excited states of 1,4,8,11,15,18,22,25-Octabutoxyphthalocyaninato-nickel(II), NiPc(BuO)(8), and the dynamics of its deactivation after excitation into the S(1)(pi,pi) state in toluene solution. According to X-ray crystallographic analysis NiPc(BuO)(8) has a highly saddled structure in the solid state. However, DFT studies suggest that in solution the complex is likely to flap from one D(2)(d)-saddled conformation to the opposite one through a D(4)(h)-planar structure. The spectral and kinetic changes for the complex in toluene are understood in terms of the 730 nm excitation light generating a primarily excited S(1) (pi,pi) state that transforms initially into a vibrationally hot (3)(d(z)2,d(x)2(-)(y)2) state. Cooling to the zeroth state is complete after ca. 8 ps. The cold (d,d) state converted to its daughter state, the (3)LMCT (pi,d(x)2(-)(y)2), which itself decays to the ground state with a lifetime of 640 ps. The proposed deactivation mechanism applies to the D(2)(d)-saddled and the D(4)(h)-planar structure as well. The results presented here for NiPc(BuO)(8) suggest that in nickel phthalocyanines the (1,3)LMCT (pi,d(x)2(-)(y)2) states may provide effective routes for radiationless deactivation of the (1,3)(pi,pi) states.     

Molecular spectroscopy for ground-state transfer of ultracold RbCs molecules

We perform one- and two-photon high resolution spectroscopy on ultracold samples of RbCs Feshbach molecules with the aim to identify a suitable route for efficient ground-state transfer in the quantum-gas regime to produce quantum gases of dipolar RbCs ground-state molecules. One-photon loss spectroscopy allows us to probe deeply bound rovibrational levels of the mixed excited (A(1)Σ(+)-b(3)Π)0(+) molecular states. Two-photon dark state spectroscopy connects the initial Feshbach state to the rovibronic ground state. We determine the binding energy of the lowest rovibrational level |v' = 0, J' = 0> of the X(1)Σ(+) ground state to be D = 3811.5755(16) cm(-1), a 300-fold improvement in accuracy with respect to previous data. We are now in the position to perform stimulated two-photon Raman transfer to the rovibronic ground state.     

Spectroscopic and excited-state properties of tri-9-anthrylborane II: Electroabsorption and electrofluorescence spectra

Electroabsorption and electrofluorescence spectroscopies were conducted for tri-9-anthrylborane (TAB) doped in poly(methyl methacrylate) films (1.0 mol %) to reveal the spectroscopic and excited-state properties of the compound. TAB showed three distinct absorption bands: bands I [(19 - 25) x 10(3) cm(-1)], II [(25-31) x 10(3) cm(-1)], and III (>31 x 10(3) cm(-1)). The electroabsorption spectrum demonstrated that the electronic transitions in bands I and III accompanied electric dipole moment changes (Deltamu), while the change in the molecular polarizability contributed mainly to electroabsorption band II. Because of the similarities of the electroabsorption spectrum of band II with that of anthracene itself, band II was assigned to the electronic transition to the locally excited (LE) state of the anthryl group. On the other hand, bands I and III were best described by the electronic transitions to the excited charge-transfer (CT) states. The study demonstrated furthermore that the Deltamu value of TAB accompanied by the lowest-energy electronic transition was as large as 7.8 D, which agreed very well with that determined by the solvent dependences of the absorption and fluorescence maximum energies of TAB (approximately 8.0 D, ref 1): Deltamu = 7.8-8.0 D. The results proved explicitly that the excited state of TAB was localized primarily on the p orbital of the boron atom. Despite the dipole moment change (Deltamu = 7.8-8.0 D) for the lowest-energy electronic transition (band I), the electrofluorescence of TAB accompanied the change in the molecular polarizability. The spectroscopic and excited-state properties of TAB including the curious behavior of the electrofluorescence spectrum as mentioned above were discussed on the basis of theoretical considerations.     

The permanent electric dipole moments of WN and ReN and nuclear quadrupole interaction in ReN

The high-resolution laser induced fluorescence spectra of tungsten mononitride WN and rhenium mononitride ReN have been recorded in a laser ablation/molecular beam spectrometer. The field free spectrum of the (0,0)A (4)Pi(3/2)-X (4)Sigma(1/2) (-) band system of (186)WN has been analyzed to produce B("), B('), and gamma(") values of 0.4659(2), 0.4554(2), and 0.0518(1) cm(-1), respectively. The permanent electric dipole moments mu for the X (4)Sigma(1/2) (-) and A (4)Pi(3/2) state were determined to be 3.77(18) and 2.45(3) D, respectively, from the analysis of the optical Stark effect. The (0,0)[26.0]0(+)-X0(+) band system of ReN was recorded in the presence of a variable static electric field. The ground and excited state electric dipole moments of (187)ReN were determined to be mu(X0(+))=1.96(8) D and mu([26.0]0(+))=3.53(4) D. Splittings in the field free (187)ReN spectrum were analyzed to produce (187)Re (I=5/2) nuclear electric quadrupole coupling constants e(2)Qq(0) of -0.0304(8) and 0.0328(9) cm(-1) for the X0(+) and [26.0]0(+) states, respectively. A molecular orbital correlation model is used to interpret the observation and a comparison is made to CrN and MoN.     

Structural and spectroscopic study of the LiRb molecule beyond the Born-Oppenheimer approximation

Adiabatic and diabatic potential energy curves and the permanent and transition dipole moments of the low-lying electronic states of the LiRb molecule dissociating into Rb(5s, 5p, 4d, 6s, 6p, 5d, 7s, 6d) + Li(2s, 2p) have been investigated. The molecular calculations are performed with an ab initio approach based on nonempirical pseudopotentials for Rb(+) and Li(+) cores, parametrized l-dependent core polarization potentials and full configuration interaction calculations. The derived spectroscopic constants (R(e), D(e), T(e), ω(e), ω(e)x(e), and B(e)) of the ground state and lower excited states are in good agreement with the available theoretical works. However, the 8-10(1)Σ(+), 8-10(3)Σ(+), 6(1,3)Π, and 3(1,3)Δ excited states are studied for the first time. In addition, to the potential energy, accurate permanent and transition dipole moments have been determined for a wide interval of internuclear distances. The permanent dipole moment of LiRb has revealed ionic characters both relating to electron transfer and yielding Li(-)Rb(+) and Li(+)Rb(-) arrangements. The diabatic potential energy for the (1,3)Σ(+), (1,3)Π, and (1,3)Δ symmetries has been performed for this molecule for the first time. The diabatization method is based on variational effective Hamiltonian theory and effective metric, where the adiabatic and diabatic states are connected by an appropriate unitary transformation.     

Ab initio dipole polarizability surfaces of water molecule: static and dynamic at 514.5 nm

Coupled cluster calculations with a carefully designed basis set have been performed to obtain both static, alpha, and dynamic at 514.5 nm, alpha(514.5 nm), dipole polarizability surfaces of water. We employed a medium size basis set (13s10p6d3f9s6p2d1f)[9s7p6d3f6s5p2d1f] consisting of 157 contracted Gaussian-type functions that yields values near the Hartree-Fock limit for alpha [G. Maroulis, J. Chem. Phys. 94, 1182 (1991)]. The alpha and alpha(514.5 nm) surfaces were able to reproduce all the experimentally available information about the dipole polarizability of water, especially the Raman spectra of gaseous H(2)O, D(2)O, and HDO. Vibrational averages for the dipole polarizability of water molecule are also reported.     

A highly sensitive method for time-resolved detection of O(1D) applied to precise determination of absolute O(1D) reaction rate constants and O(3P) yields

We demonstrate detection, in the gas-phase, of O(1D2) at concentrations down to 10(7) cm(-3) and develop this new method for time-resolved kinetic studies allowing both the total removal rate of O(1D2), of up to 1.5 x 10(6) s(-1), and the fraction quenched to O(3P(J)) by species X, k(q)/k(X), to be determined precisely from a single time profile: at 295 K we find, k(O(1D2) + N2O) = (1.43 +/- 0.08) x 10(-10) cm3 s(-1) with k(q)/k(N2O) = 0.056 +/- 0.009; k(O(1D2) + C2H2) = (3.1 +/- 0.2) x 10(-10) cm3 s(-1) with k(q)/k(C2H2) = 0.020 +/- 0.010; k(q)/k(H2O) < 0.003 for O(1D2) + H2O.     

The permanent electric dipole moment of calcium monodeuteride

The sub-Doppler laser induced fluorescence spectra of numerous branch features in the B 2Sigma+ -X 2Sigma+(0,0) band of calcium monodeuteride were recorded field-free and in the presence of a static electric field of up to 7 kV/cm. The field-free spectra were analyzed to produce an improved set of fine structure parameters for the B 2Sigma+(v=0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments of 2.57(3) and 2.51(3) D for B 2Sigma+(v=0) and X 2Sigma+(v=0) states, respectively. The permanent electric dipole moment for the X 2Sigma+(v=0) state of CaH is estimated to be 2.53(3) D.     

Ground state potential energy curve and dissociation energy of MgH

New high-resolution visible emission spectra of the MgH molecule have been recorded with high signal-to-noise ratios using a Fourier transform spectrometer. Many bands of the A 2Pi-->X 2Sigma+ and B' 2Sigma+-->X 2Sigma+ electronic transitions of 24MgH were analyzed; the new data span the v' = 0-3 levels of the A 2Pi and B'2Sigma+ excited states and the v'=0-11 levels of the X 2Sigma+ ground electronic state. The vibration-rotation energy levels of the perturbed A 2Pi and B' 2Sigma+ states were fitted as individual term values, while those of the X 2Sigma+ ground state were fitted using the direct-potential-fit approach. A new analytic potential energy function that imposes the theoretically correct attractive potential at long-range, and a radial Hamiltonian that includes the spin-rotation interaction were employed, and a significantly improved value for the ground state dissociation energy of MgH was obtained. The v'=11 level of the X 2Sigma+ ground electronic state was found to be the highest bound vibrational level of 24MgH, lying only about 13 cm(-1) below the dissociation asymptote. The equilibrium dissociation energy for the X 2Sigma+ ground state of 24MgH has been determined to be De=11104.7+/-0.5 cm(-1) (1.37681+/-0.00006 eV), whereas the zero-point energy (v'=0) is 739.11+/-0.01 cm(-1). The zero-point dissociation energy is therefore D0=10365.6+/-0.5 cm(-1) (1.28517+/-0.00006 eV). The uncertainty in the new experimental dissociation energy of MgH is more than 2 orders of magnitude smaller than that for the best value available in the literature. MgH is now the only hydride molecule other than H2 itself for which all bound vibrational levels of the ground electronic state are observed experimentally and for which the dissociation energy is determined with subwavenumber accuracy.