Physical Review A

Shift and broadening of resolved hydrogen Balmer- α fine-structure lines in helium

E. W. Weber

Published Dec 1, 1979• 29 citations

Abstract

Accurate values for the density shift and broadening of five isolated ${\mathrm{H}}_{\ensuremath{\alpha}}$ fine-structure transitions have been measured. Doppler-free polarization and double-quantum saturation spectroscopy with a cw dye laser are used in a He dc discharge with 1% ${\mathrm{H}}_{2}$. The negative shifts and the huge broadening values are correctly predicted by an impact-approximation theory taking into account the large cross sections for fine-structure transfer (quenching) collisions and only Van der Waals interaction between ${\mathrm{H}}^{*}$ and He. Consequences of a comparison with the positive shift of the unresolved ${\mathrm{H}}_{\ensuremath{\alpha}}$ line and of the alkali-metal $D$ lines in He buffer gas are discussed. For pressures below 0.1 Torr hfs decoupling collisions give rise to a positive shift of single ${\mathrm{H}}_{\ensuremath{\alpha}}$ fine-structure lines and to a collisional narrowing effect analogous to that observed in nuclear magnetic resonance.

DOI: 10.1103/physreva.20.2278

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Broadening of the D Lines and the Relaxation of the Resonance Levels of Sodium Due to Collisions with Helium

E L Lewis, L. F. McNamara

Physical Review AJun 1, 197265 citations

Double-Quantum Saturation Spectroscopy in Hydrogen: Measurement of the 3P32−3D32 Lamb Shift

E. W. Weber, J. E. M. Goldsmith

Physical Review LettersOct 2, 197817 citations

Fine-structure effects on collisional broadening and shift of thallium two-photon lines

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Physical Review AOct 1, 19961 citation

Comprehensive theory for line broadening in high-resolution and nonlinear spectroscopies: application to the Na D lines

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Coupled-channel analysis of collisional effects on HFS transitions in antiprotonic helium atoms

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S. Saoudi, Ch. Lerminiaux, M. Dumont

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Physical Review A

Shift and broadening of resolved hydrogen Balmer- α fine-structure lines in helium

E. W. Weber

Published Dec 1, 1979• 29 citations

Publisher

Abstract

Accurate values for the density shift and broadening of five isolated

{\mathrm{H}}_{\ensuremath{\alpha}}

fine-structure transitions have been measured. Doppler-free polarization and double-quantum saturation spectroscopy with a cw dye laser are used in a He dc discharge with 1%

{\mathrm{H}}_{2}

. The negative shifts and the huge broadening values are correctly predicted by an impact-approximation theory taking into account the large cross sections for fine-structure transfer (quenching) collisions and only Van der Waals interaction between

{\mathrm{H}}^{*}

and He. Consequences of a comparison with the positive shift of the unresolved

{\mathrm{H}}_{\ensuremath{\alpha}}

line and of the alkali-metal

D

lines in He buffer gas are discussed. For pressures below 0.1 Torr hfs decoupling collisions give rise to a positive shift of single

{\mathrm{H}}_{\ensuremath{\alpha}}

fine-structure lines and to a collisional narrowing effect analogous to that observed in nuclear magnetic resonance.

DOI: 10.1103/physreva.20.2278

Related papers

Broadening of the D Lines and the Relaxation of the Resonance Levels of Sodium Due to Collisions with Helium

E L Lewis, L. F. McNamara

Calculated potentials for the NaHe molecule are used to obtain collision-induced widths and shifts for the sodium $D$ lines together with cross sections for fine-structure transitions and the relaxation of the multipole polarizations of the resonance levels. The atomic collision is treated in an adiabatic approximation in which the colliding atoms form a molecular system which rotates during the collision. We find the resonance lines to be broadened equally and to be approximately 70% wider, and with associated shifts of an order of magnitude smaller, than expected on the basis of van der Waals forces. The dependence of the cross sections for relaxation of the multipole polarizations of the resonance levels on the molecular-coupling conditions and the rotation of the system during collision is discussed and indicates a limitation on the sum rule for these cross sections. Good over-all agreement with the existing experimental data is obtained.Calculated potentials for the NaHe molecule are used to obtain collision-induced widths and shifts for the sodium $D$ lines together with cross sections for fine-structure transitions and the relaxation of the multipole polarizations of the resonance levels. The atomic collision is treated in an adiabatic approximation in which the colliding atoms form a molecular system which rotates during the collision. We find the resonance lines to be broadened equally and to be approximately 70% wider, and with associated shifts of an order of magnitude smaller, than expected on the basis of van der Waals forces. The dependence of the cross sections for relaxation of the multipole polarizations of the resonance levels on the molecular-coupling conditions and the rotation of the system during collision is discussed and indicates a limitation on the sum rule for these cross sections. Good over-all agreement with the existing experimental data is obtained.

Physical Review AJun 1, 197265 citations

Double-Quantum Saturation Spectroscopy in Hydrogen: Measurement of the 3P32−3D32 Lamb Shift

E. W. Weber, J. E. M. Goldsmith

Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He- ${\mathrm{H}}_{2}$ dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that $3{D}_{\frac{3}{2}}$ lies lower than the $3{P}_{\frac{3}{2}}$ state. Further applications of the method are discussed.Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He-${\mathrm{H}}_{2}$ dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that $3{D}_{\frac{3}{2}}$ lies lower than the $3{P}_{\frac{3}{2}}$ state. Further applications of the method are discussed.

Physical Review LettersOct 2, 197817 citations

Fine-structure effects on collisional broadening and shift of thallium two-photon lines

G. Mahr, G. Hermann

Broadening and shift rates by rare gases have been measured for the Tl transitions 6 ${\mathit{P}}_{1/2}$ - ${\mathit{nP}}_{1/2,3/2}$ (n=9-14) applying Doppler-free two-photon spectroscopy. The rates show a clearly significant dependence on the total angular momentum of the upper nP states and also a distinct behavior over the most interesting range of intermediate effective principle quantum numbers. Calculations using a van der Waals potential and a combination of polarization and Fermi pseudopotential describe these dependences well. \textcopyright{} 1996 The American Physical Society.Broadening and shift rates by rare gases have been measured for the Tl transitions 6${\mathit{P}}_{1/2}$-${\mathit{nP}}_{1/2,3/2}$ (n=9-14) applying Doppler-free two-photon spectroscopy. The rates show a clearly significant dependence on the total angular momentum of the upper nP states and also a distinct behavior over the most interesting range of intermediate effective principle quantum numbers. Calculations using a van der Waals potential and a combination of polarization and Fermi pseudopotential describe these dependences well. \textcopyright{} 1996 The American Physical Society.

Physical Review AOct 1, 19961 citation

Comprehensive theory for line broadening in high-resolution and nonlinear spectroscopies: application to the Na D lines

R. M. Herman, E. W. Weber

A general method for analysing line broadening caused by Doppler, phaseshift, inelastic and velocity-changing collisional effects is proposed for transitions at optical wavelengths. In a unified approach Poisson statistics are used to describe collision probabilities randomly distributed in a time interval which can terminate the optical coherence in a combination of the above effects; markoffian independence is assumed for each collision. Then the dipole moment correlation function is obtained in a form which is virtually exact in accounting for all effects of isotropic forces, and which is correct to second-order terms in the anisotropic interaction potentials. Phenomena as diverse as standard optical pressure broadening, broadening due to velocity-changing collisions in nonlinear spectroscopies, and Dicke narrowing of the Doppler contour are described. The implications of the theory are discussed in detail and applied to the case of the NaD lines perturbed by He buffer gas. Numerical calculations reveal that the substantially different lineshift and broadening parameters in nonlinear and in standard optical spectroscopies can be reasonably well understood within the limitations posed by present uncertainties in the Na 3 2 P-He interaction potentials. However, the large differences in shift and width between the D 2 and D 1 lines in saturation spectroscopy cannot be explained within the present theory.A general method for analysing line broadening caused by Doppler, phaseshift, inelastic and velocity-changing collisional effects is proposed for transitions at optical wavelengths. In a unified approach Poisson statistics are used to describe collision probabilities randomly distributed in a time interval which can terminate the optical coherence in a combination of the above effects; markoffian independence is assumed for each collision. Then the dipole moment correlation function is obtained in a form which is virtually exact in accounting for all effects of isotropic forces, and which is correct to second-order terms in the anisotropic interaction potentials. Phenomena as diverse as standard optical pressure broadening, broadening due to velocity-changing collisions in nonlinear spectroscopies, and Dicke narrowing of the Doppler contour are described. The implications of the theory are discussed in detail and applied to the case of the NaD lines perturbed by He buffer gas. Numerical calculations reveal that the substantially different lineshift and broadening parameters in nonlinear and in standard optical spectroscopies can be reasonably well understood within the limitations posed by present uncertainties in the Na 3 2 P-He interaction potentials. However, the large differences in shift and width between the D 2 and D 1 lines in saturation spectroscopy cannot be explained within the present theory.

Journal of Physics B Atomic and Molecular PhysicsApr 28, 19838 citations

Coupled-channel analysis of collisional effects on HFS transitions in antiprotonic helium atoms

Grigory Ya. Korenman, S. N. Yudin

Collisions of metastable antiprotonic helium with atoms of a medium induce transitions between hyperfine structure sublevels as well as shifts and broadenings of the microwave M1 spectral lines. We consider these phenomena in the framework of a model with scalar and tensor interactions between and He atoms. S -matrix is obtained by solving coupled-channels equations involving 4 HFS sublevels ( F = L ± 1/2, J = F ± 1/2) of the nL level and relative angular momenta up to l = 5 at the kinetic energy E ≲ 25 K. The inelastic cross sections are less than elastic ones by four orders of value for the single electron or antiproton spin-flip transitions (Δ J = ±1, Δ F = 0, ± 1) and by seven orders of value for the double spin-flip transitions (Δ J = 0, ± 2, Δ F = ±1). The cross sections show a resonance behaviour at very low energy ( E ∼ 1–4 K). The results for the relaxation rate λ( F − → F + ), the frequency shift and broadening of the M1 spectral lines for the favoured transitions (Δ F = ±1, Δ J = ±1) are compatible with the recent experimental data obtained by a triple (laser–microwave–laser) resonance method at T = 6 K. The calculated values are lowered by a factor of 1.5–2 with the temperature rising up to 25 K.Collisions of metastable antiprotonic helium with atoms of a medium induce transitions between hyperfine structure sublevels as well as shifts and broadenings of the microwave M1 spectral lines. We consider these phenomena in the framework of a model with scalar and tensor interactions between and He atoms. S -matrix is obtained by solving coupled-channels equations involving 4 HFS sublevels ( F = L ± 1/2, J = F ± 1/2) of the nL level and relative angular momenta up to l = 5 at the kinetic energy E ≲ 25 K. The inelastic cross sections are less than elastic ones by four orders of value for the single electron or antiproton spin-flip transitions (Δ J = ±1, Δ F = 0, ± 1) and by seven orders of value for the double spin-flip transitions (Δ J = 0, ± 2, Δ F = ±1). The cross sections show a resonance behaviour at very low energy ( E ∼ 1–4 K). The results for the relaxation rate λ( F − → F + ), the frequency shift and broadening of the M1 spectral lines for the favoured transitions (Δ F = ±1, Δ J = ±1) are compatible with the recent experimental data obtained by a triple (laser–microwave–laser) resonance method at T = 6 K. The calculated values are lowered by a factor of 1.5–2 with the temperature rising up to 25 K.

arXiv:nucl-th/0411077Journal of Physics B Atomic Molecular and Optical PhysicsMar 6, 200621 citations

Collisional Narrowing of a Fine-Structure Raman Transition

S. Saoudi, Ch. Lerminiaux, M. Dumont

The line shape of the Raman transition between metastable levels of neon ( $^{3}p_{0}\mathrm{and}^{3}p_{2}$ ) is studied as a function of the pressure of a helium buffer gas. Dicke narrowing of the Doppler-broadened nonresonant Raman signal (for large optical detunings) gives the first evidence of conservation of a fine-structure coherence by velocity-changing collisions. Pressure broadening of the resonant Raman signal gives a measurement of the velocity-changing-collision rate.The line shape of the Raman transition between metastable levels of neon ($^{3}p_{0}\mathrm{and}^{3}p_{2}$) is studied as a function of the pressure of a helium buffer gas. Dicke narrowing of the Doppler-broadened nonresonant Raman signal (for large optical detunings) gives the first evidence of conservation of a fine-structure coherence by velocity-changing collisions. Pressure broadening of the resonant Raman signal gives a measurement of the velocity-changing-collision rate.

Physical Review LettersMay 19, 19866 citations

Accurate values for the density shift and broadening of five isolated

{\mathrm{H}}_{\ensuremath{\alpha}}

fine-structure transitions have been measured. Doppler-free polarization and double-quantum saturation spectroscopy with a cw dye laser are used in a He dc discharge with 1%

{\mathrm{H}}_{2}

{\mathrm{H}}^{*}

and He. Consequences of a comparison with the positive shift of the unresolved

{\mathrm{H}}_{\ensuremath{\alpha}}

line and of the alkali-metal

D

lines in He buffer gas are discussed. For pressures below 0.1 Torr hfs decoupling collisions give rise to a positive shift of single

{\mathrm{H}}_{\ensuremath{\alpha}}

fine-structure lines and to a collisional narrowing effect analogous to that observed in nuclear magnetic resonance.

Calculated potentials for the NaHe molecule are used to obtain collision-induced widths and shifts for the sodium

D

lines together with cross sections for fine-structure transitions and the relaxation of the multipole polarizations of the resonance levels. The atomic collision is treated in an adiabatic approximation in which the colliding atoms form a molecular system which rotates during the collision. We find the resonance lines to be broadened equally and to be approximately 70% wider, and with associated shifts of an order of magnitude smaller, than expected on the basis of van der Waals forces. The dependence of the cross sections for relaxation of the multipole polarizations of the resonance levels on the molecular-coupling conditions and the rotation of the system during collision is discussed and indicates a limitation on the sum rule for these cross sections. Good over-all agreement with the existing experimental data is obtained.

Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He-

{\mathrm{H}}_{2}

dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that

3{D}_{\frac{3}{2}}

lies lower than the

3{P}_{\frac{3}{2}}

state. Further applications of the method are discussed.

Broadening and shift rates by rare gases have been measured for the Tl transitions 6

{\mathit{P}}_{1/2}

{\mathit{nP}}_{1/2,3/2}

(n=9-14) applying Doppler-free two-photon spectroscopy. The rates show a clearly significant dependence on the total angular momentum of the upper nP states and also a distinct behavior over the most interesting range of intermediate effective principle quantum numbers. Calculations using a van der Waals potential and a combination of polarization and Fermi pseudopotential describe these dependences well. \textcopyright{} 1996 The American Physical Society.

The line shape of the Raman transition between metastable levels of neon (

^{3}p_{0}\mathrm{and}^{3}p_{2}

) is studied as a function of the pressure of a helium buffer gas. Dicke narrowing of the Doppler-broadened nonresonant Raman signal (for large optical detunings) gives the first evidence of conservation of a fine-structure coherence by velocity-changing collisions. Pressure broadening of the resonant Raman signal gives a measurement of the velocity-changing-collision rate.