Showing papers on "Stark effect published in 1974"

Observation of the resonant Stark effect at optical frequencies

Abstract: The spectrum of resonantly scattered light at right angles to a sodium atomic beam is reported. The light source was a cw dye laser tuned to resonance with a hyperfine component of the Dz line, and incident at right angles to the atomic beam. The spectrum, with the Stark effect sidebands, was recorded as a function of both the laser intensity and its detuning from resonance. The overall resolution is better than 20 MHz.

Weyl's theory applied to the Stark effect in the hydrogen atom

Abstract: A short review of Hermann Weyl's theory for singular second-order differential equations is given and its numerical aspects are discussed. It is pointed out that this method is suitable for the treatment of perturbations which make the spectrum continuous. The Stark effect on the ground state of the hydrogen atom is taken as an example. The spectral density, the imaginary part of Weyl's "$m$ function," is calculated numerically using Runge-Kutta integration and Airy integrals for the asymptotic region. Showing $\ensuremath{\delta}$-function-like behavior with poles of $m$ on the real axis for the discrete levels, the spectral density involves approximate Lorentzians for the metastable states of the continuous spectrum, corresponding to poles of $m$ in the complex plane. Trajectories of these poles for electric fields up to 0.25 a.u. are shown for the one-dimensional as well as for the full three-dimensional problem.

Direct Spectroscopic Observation of Electrons in Image-Potential States Outside Liquid Helium

Abstract: We present the first direct spectroscopic study of electrons bound in image-potential-induced surface states outside liquid helium. We have observed absorption lines which show the expected linear Stark effect in the presence of an electric field. Zero-field splittings extrapolated from the data are 125.9 and 148.6 GHz for electronic transitions from the ground state to the first two excited states in the image-potential well.

Fine structure, hyperfine structure, and Stark effect in the NO A 2Σ+ state by optical radio‐frequency double resonance

Abstract: Using the Se I 1961 A spectral line to pump the J = 3/2 component of the v = 3, N = 1 level of the NO A 2Σ+ state, we observe the zero‐field rho‐doubling hyperfine transitions by optical radio‐frequency double resonance. The Stark shift of one of the resonance components is measured to determine the permanent electric dipole moment. An analysis of the resonance line shapes yields the following molecular constants: The rho‐doubling constant γ = −82.91±0.03 MHz; the hyperfine parameters of the 14N nucleus b = 40.29±0.07 MHz, c = 2.25±0.11 MHz, and eqQ = −2.88±0.17 MHz; and the dipole moment μ = 1.10±0.03 D, where all errors represent three standard deviations. The value of γ is explained reasonably well by calculations of the A−X spin‐orbit mixing from which we conclude that variations of γ with v and N are small. The values of the hyperfine parameters b and c are within 6% and 18% of recent CI calculations by S. Green, while the less well determined values of eqQ differ by about a factor of 2. The measured dipole moment differs considerably from the CI value, μ = 0.40±0.10 D. We speculate on possible explanations for this surprisingly large discrepancy.

THE DIPOLE MOMENT IN THE LOWEST SINGLET π*→π STATE OF INDOLE DETERMINED BY THE OPTICAL STARK EFFECT*

Abstract: — A Stark effect is observed in the rotational fine structure of the 0–0 band of the lowest π*π state of indole. This yields a dipole moment change |ΔμA| = 0·14±0·05. D. Evidence is presented which indicates that the sign of ΔμA is positive. An increase of dipole moment on excitation is in agreement with the value (+ 0·06 D) corresponding to the previously calculated orbitals of Song and Kurtin. The direction of the transition moment, calculated from the results of rotational analysis published by Mani and Lombardi, is found to be 26° from the molecular A-axis.

Rotational isomerism, barrier to internal rotation and electric dipole moment of acrylic acid by microwave spectroscopy

Abstract: Microwave spectra have been observed for the normal and acid deuterated isotopic species of the s-cis and s-trans rotamers of acrylic acid in the ground and a number of excited torsional states. Both rotameric forms are planar with the hydroxyl group adopting the cis conformation relative to the carbonyl group. The dipole moments determined from Stark effect measurements are [graphic omitted].The difference in zero point vibrational energy between the two rotamers and the 1 â†� 0 torsional frequencies have been determined from relative intensity measurements as E°s-trans—E°s-cis= 58 ± 20 cm–1, νs-cis= 105 ± 20 cm–1, νs-trans= 95 ± 20 cm–1. The potential function hindering the internal rotation is essentially two-fold with a barrier of 1340 ± 500 cm–1(16.0 ± 6.0 kJ mol–1) at an angle of 89 ± 4° from the s-cis configuration.

Molecular Zeeman effect, electric dipole moment, and boron nuclear hyperfine coupling constants in HBS

Abstract: The zero‐field microwave spectra of the J =0 → J = 1 transitions in H11B32S, D11B32S, and D10B32S have been observed under high resolution to give the boron nuclear quadrupole coupling constants of eqQ = −3.72±0.03 MHz for 11B and eqQ = −7.91±0.03 MHz for 10B and the nuclear magnetic spin rotation constants along the axis perpendicular to the internuclear axis of M⊥=−7.2 ± 3.0 kHz for 11B and 1M⊥=−2.6 ± 1.0 kHz for 10B. The magnitude of the electric dipole moment was measured by high electric fields (Stark effect) to give |μ| = 1.298 ± 0.005 D. High magnetic fields (Zeeman effect) were used to measure the molecular g values and magnetic susceptibility anisotropies. The results are g⊥=−0.0414 ± 0.0002 and χ⊥−χ∥=7.2 ± 0.5 × 10−6 erg/G2· mole for H11B32S and g⊥=−0.0356 ± 0.0002 and χ⊥−χ∥=9.8 ± 2.1 × 10−6 erg/G2· mole for D11B32S. The resultant molecular electric quadrupole moment is Q∥ =2.7±0.6 × 10−26 esu · cm2 and the g values from the H11B32S–D11B32S isotopic pair were used to determine the sign of the el...

Microwave spectrum, dipole moment, and conformation of 2,3‐dihydro‐p‐dioxin(1,4‐dioxene)

Abstract: The microwave spectrum of 2,3‐dihydro‐p‐dioxin(1,4‐dioxene) has been studied in the R‐band range (26.5–40.0 GHz) using a Hewlett‐Packard model 8400 Stark modulated spectrometer. The rotational constants for the ground state and four vibrationally excited states have been derived from fitting b‐type, low J R ‐branch transitions. The rotational constants for the ground state are (in megahertz) A = 5697.703±0.010; B = 4968.410±0.008; C = 2865.181±0.010. The presence of a C 2 symmetry axis has been established by analysis of the Stark effect yielding a single nonzero component of the dipole moment μ b = 0.939±0.008 D and by the effect of nuclear spin statistical weights on the relative intensities of the rotational transitions. That the symmetry point group is C 2 rather than C 2v is established by the value of (1/2)(Ia + Ib − Ic ) which is clearly too large for the C 2v structure. Model calculations to reproduce the rotational constants show that they are particularly sensitive to two structural parameters: the C=C–O angle (123.4±0.5°) and the twist angle, i.e., the angle between the C=C bond and C–C bond (29.9±1.5°). Consideration of the ring angles for a structure derived by diagnostic least squares shows little, if any, ring strain.

Stark broadening parameters of Si I, Si II and Si III lines

Abstract: Spectral lines emited by first three ionisation species of silicon were studyed in a wide range of plasma parameters. The silicon was present as an impurity in the argon plasma created in an electromagneticT tube. Four various condenser bank energies give the plasma in a range of temperatures 8700 to 16400°K and electron concentrations 2.95·1017 cm−3to 5.6·1017 cm−3.

Interference pulses in optical free induction decay

Abstract: A new feature of optical free induction decay (FID) is observed in a coherently prepared sample of $^{13}\mathrm{CH}$$_{3}\mathrm{F}$ by the method of Stark switching. The preparative phase is due to the resonant steady-state excitation by a cw laser beam, and is followed by FID upon sudden application of a dc Stark field that switches the molecular sample out of resonance. The emission is not observed as a simple decay but instead appears as a train of sharp pulses regularly spaced in time as a result of a repetitive interference. This situation arises because an entire set of infrared transitions within the Stark split manifold are initially prepared, in contrast to our previous study of a nondegenerate transition. The emission, which beats with the laser, produces a heterodyne beat spectrum, consisting of a set of regularly spaced frequencies, that is the Fourier transform of the slowly decaying pulse progression observed. We thus demonstrate what is the optical analog of the well-known NMR method of high-resolution pulse Fourier spectroscopy. The detailed behavior of the pulse train agrees well with an FID theory that assumes the transitions to be uncoupled. The subtle behavior of FID near the time origin is explored also by approximate analytic expressions that reveal either a near zero amplitude or sizable amplitude depending on the degree of saturation in the preparative stage. The experimental technique discussed offers an attractive way for obtaining high-resolution optical spectra without Doppler broadening, and for generating an optical pulse train whose time scale can be compressed by simply increasing the Stark field.

Microwave spectrum, structure, and dipole moment of 2,3,4,5‐tetracarbahexaborane(6)

Abstract: The structure of 2,3,4,5‐tetracarbahexaborane (C4B2H6) has been determined from the microwave spectra of 10 isotopic species. The pentagonal pyramidal geometry of the molecule has been confirmed. The four carbon atoms lie in the pentagonal base; the short C–C bond lengths (1.43 A) suggest pi‐bonding character. A molecular dipole moment of 2.26 ± 0.06 D was determined from the observed Stark effect.

Molecular beam electric resonance spectroscopy

Abstract: Publisher Summary Beam spectroscopy has provided much of what is known about the fine structure of atoms, the hyperfine structures and g values of atoms and molecules, and the values of nuclear spins and moments. This chapter summarizes what has been achieved with molecular beam electric resonance (MBER) spectroscopy. The operation of a molecular beam resonance spectrometer is shown. The field (say, A field) of the spectrometer selects molecules in the desired quantum state; the beam then goes to a region (say C field) in which transitions to other quantum states may be induced, and the beam subsequently passes through B field quantum state selector to a detector. In contrast to the mode of operation of the usual absorption spectrometer, it is the flux of molecules, rather than the intensity of radiation, which is monitored: those changes are looked for in the flux of molecules, which can be correlated with the frequency of the radiation in the C field.

Influence of ion dynamics on Hα and Hβ at low densities

Abstract: Calculations for the Stark broadening of H alpha and H beta using a unified theory for both ions and electrons are presented in the density range 1014 to 1015 cm-3 at a temperature of 104 K. Although the theory is of marginal validity at these densities, it shows quite conclusively the influence of ion dynamics in reducing the dip at the centre of the H beta profile and the peak in the centre of the H alpha profile.

High-density Stark profiles of two neutral helium lines and their forbidden components

Abstract: Measured and calculated profiles are compared for two neutral helium lines, He I (4471 and 6678 A), and their forbidden components at high electron densities. Calculations were done at the measured plasma conditions and are compared directly with the experimental profiles. Good agreement is found between theory and experiment.

The Microwave Spectrum of Trifluoromethyl Hypofluorite

Abstract: The microwave spectrum of trifluoromethyl hypofluorite (CF3OF) has been analyzed in the region 8–40 GHz. Only μa R-type transitions were observed despite a careful search and using double-resonance techniques. These determine the following rotational constants: A = 5600 ± 100, B = 3108.13 ± 0.02, C = 3049.25 ± 0.02 MHz. The dipole moments determined from Stark effect measurements are μa = 0.30 ± 0.02, μb = 0.10 ± 0.06, μc = 0 D. The υ = 1 state of the CF3 torsion has also been measured; relative intensity measurements lead to a potential barrier of 3.9 kcal/mol, somewhat higher than the electron diffraction results.

Vibrational dependence of the dipole moment in the A3Π1 state of ICI

Abstract: The Stark effect is measured for the A3Π1←1Σ+ band system. The dipole moment of the A state as a function of vibrational level is measured to be, in Debye, ν′μ′ν′μ′ν′μ′ν′μ′72.00(± 0.15)111.85(0.10)141.75(0.05)211.15(0.15)91.95(0.05)121.80(0.10)171.50(0.15)250.6 (0.15)101.90(0.10)131.60(0.15)181.25(0.10)270.6 (0.15) The sign of the A state moments appears to be opposite to that of the X state.

QED calculation of the resonant Stark effect

Abstract: Quantum electrodynamic calculations involving the resonant Stark effect are reported. By including the effects of multiple spontaneous emissions for a two-level atom in a resonant applied field solutions are obtained which are valid over many radiative lifetimes. The resonance fluorescence spectrum is also calculated as a function of the detuning parameter. The theoretical results are in agreement with the experimentally observed long term fluorescence spectrum.

Experimental Study of Stark Broadening of the Allowed and Forbidden Transitions 23P-43D, 4 3F (λ=4471.5 Å, λ=4470 Å) in Neutral Helium

Abstract: Measurements were made of the profile of the Hel 4471.5 Å line and its forbidden component at λ = 4469.9 Å, emitted from an afterglow plasma of electron densities in the range 2.2 × 1014 to 1.5 × 1015 cm-3. The various quantities which define position and form of the profile have been compared with the theoretical calculations of Griem and of Barnard et al. It has been found that the wavelength shifts of the individual components and, thus, the peak separation are slightly smaller than predicted by theory, whereas the intensity in the valley between the two components is found to be slightly larger than the theoretical values. The peak intensity of the forbidden component is smaller than given by theory but not as small as found by D. D. Burgess and C. J. Cairns. At low electron densities the intensity of the forbidden component is proportional to the square of the normal field strength F0 of the electric microfield. At higher electron densities the intensity increases proportionally to F0 in agreement with the transition from quadratic to linear Stark effect at higher electric field strengths. The measurements show that the influence of the ion dynamics on the line profile is probably not as large as assumed by D. D. Burgess. The measurements show that the position of the intensity minimum between allowed and forbidden component is shifted towards the allowed component when the temperature decreases.

Microwave spectrum of tert-butyl mercaptan

Abstract: The spectrum of the ground vibrational state of t‐butyl mercaptan from 8 to 40 GHz has been measured and assigned using a computer controlled spectrometer. The spectrum consists of many long Q‐branch series arising from the perpendicular component of the dipole moment and also parallel R‐branch groupings at intervals of B+C. The molecule is a near prolate symmetric top with energy level splittings of several gigahertz due to the internal rotation about the C–S bond. A computer program utilizing the IAM in a form suited for the intermediate to low barrier case has been written and used to obtain a satisfactory fit of the observed spectrum to the simple rigid top‐rigid frame Hamiltonian with six adjustable parameters: A, B, C, ρ, β, and Δ0. The barrier obtained (1742 cal/mole) is significantly larger than the previously determined microwave value for methyl mercaptan and is also greater than the recent far infrared estimates for t‐butyl mercaptan. Measurements of the Stark effect for several transitions has permitted determination of the magnitudes and (because of interference effects between the internal rotation and Stark perturbations) the relative sign of the two components of the dipole moment. The direction of the dipole moment vector thus obtained is consistent with the only physically reasonable choice in this molecule.

Microwave spectrum of (fluoromethyl)germane, CH2FGeH3

Abstract: Microwave spectra of three isotopic species of CH2FGeH3 have been investigated in the region 8000–30 000 MHz. The height of the potential barrier hindering the germyl group (GeH3) internal rotation was determined to be 1390±40 cal/mole from measured A‐E frequency differences, using a PAM calculation through fourth‐order perturbations. Dipole moment components μa = 1.00 D, μb = 1.30 D, giving a resultant μ = 1.64±0.03 D, were obtained from Stark effect measurements. A technique for assigning R‐branch asymmetric rotor transitions is discussed.

Spectra and structure of small ring compounds. XXXI Microwave, Raman and infrared spectra, conformation, dipole moment, and quadrupole coupling constants of 2‐oxazoline

Abstract: The microwave spectrum of 2‐oxazoline has been recorded from 12.4–40.0 GHz. Both Q‐branch and R‐branch assignments have been made for the ground and five vibrationally excited states of the ring puckering mode for both A ‐ and B‐type transitions. The components of the diple moment were determined by the Stark effect to be μa = 1.14±0.01, μb = 1.35±0.01, μc = 0.00±0.00, and μt = 1.77±0.01 D. The quadrupole coupling constants were found to have the following values: χa a = −3.54, χb b = 2.03, and χc c = 1.51 MHz. From the inertial defect Δc and the dipole moment, it is concluded that the heavy atom skeleton is planar. From the relative intensity measurements, the first excited state of the ring puckering vibration was found to have a frequency of 79±8 cm−1 and from a series of difference bands in the infrared spectrum, the ν = 0→1, 1→2, 2→3, 3→4, and 4→5 transitions were found to have the following frequencies: 74, 95, 103, 110, and 117 cm−1, respectively. The potential function governing the ring puckering...

High-Resolution Stark Spectroscopy in the nu(4) Band of NH(3) Using a Thin-Film Diode Laser.

Abstract: Thin-film PbTe diode lasers are used for Doppler-limited Stark spectroscopy on the vibration-rotation ν4 band of 1545–1595-cm−1 region. The lasers operate cw below 20 K and are frequency tuned by varying the diode current. The ν4 excited state dipole moment of NH3 is found to be about 1% less than the ground state value.