Doppler-free multi-photon ionization: a proposal for enhancing ion images

Pomerantz, Andrew E.; Zare, Richard N.

doi:10.1016/s0009-2614(03)00158-1

Cited by 21 publications

(16 citation statements)

References 19 publications

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“…While Doppler broadening can be overcome by using two counterpropagating UV laser pulses for the REMPI detection, 7 we chose to use only one pulse ͑⌬ Ϸ 5 ns͒ for most of the present work and scan its wavelength over the Doppler profile. Because the speeds of product HD molecules formed under the current experimental conditions are moderate ͑compared to the speeds of the reactant H atoms͒ the potential signal-to-noise ratio enhancement achievable by Doppler-free spectroscopy is limited, 14 and the alignment of a third laser beam would require additional efforts. In cases where the probe laser beam could be used for photolysis at the desired wavelength ͑jЈ =2 at 1.73 eV and jЈ = 6 at 1.69 eV͒, two-color Doppler-free REMPI as described in Ref.…”

Section: Methodsmentioning

confidence: 99%

Differential cross section for the H+D2→HD(v′=1,j′=2,6,10)+D reaction as a function of collision energy

Koszinowski

Goldberg

Zhang

et al. 2007

The Journal of Chemical Physics

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We have measured differential cross sections (DCSs) for the HD (v(')=1,j(')=2,6,10) products of the H+D(2) exchange reaction at five different collision energies in the range 1.48< or =E(coll)< or =1.94 eV. The contribution from the less energetic H atoms formed upon spin-orbit excitation of Br in the photolysis of the HBr precursor is taken into account for two collision energies, E(coll)=1.84 and 1.94 eV, allowing us to disentangle the two different channels. The measured DCSs agree well with new time-dependent quantum-mechanical calculations. As the product rotational excitation increases, the DCSs shift from backward to sideward scattering, as expected. We also find that the shapes of the DCSs show only a small overall dependence on the collision energy, with a notable exception occurring for HD (v(')=1,j(')=2), which appears bimodal at high collision energies. We suggest that this feature results from both direct recoil and indirect scattering from the conical intersection.

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Section: Methodsmentioning

confidence: 99%

Differential cross section for the H+D2→HD(v′=1,j′=2,6,10)+D reaction as a function of collision energy

Koszinowski

Goldberg

Zhang

et al. 2007

The Journal of Chemical Physics

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“…II B͒. 39 Doppler-free spectroscopy ionizes H atoms irrespective of their speed in the direction of the laser propagation, thereby strongly increasing the signal without affecting the background. Enhanced signal-tobackground ratios are particularly important for studying systems with inherently small signals, such as bimolecular reactions.…”

Section: B Doppler-free Spectroscopymentioning

confidence: 99%

Construction and calibration of an instrument for three-dimensional ion imaging

Koszinowski

Goldberg

Pomerantz

et al. 2006

The Journal of Chemical Physics

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We describe a new instrument based on a delay-line detector for imaging the complete three-dimensional velocity distribution of photoionized products from photoinitiated reactions. Doppler-free [2+1] resonantly enhanced multiphoton ionization (REMPI) of H and D atoms formed upon photolysis of HBr and DBr in the range 203 nm < or = lambda photolysis < or = 243 nm yields radial speeds measured to be accurate within 1% of those calculated. The relative speed resolution is about 5% and limited by photoionization recoil broadening. A relative speed resolution of 3.4% is obtained for [3+1] REMPI, which minimizes the ionization recoil. We also determine the branching ratio between ground-state and spin-orbit-excited product channels and their associated anisotropies. We find that DBr photolysis dynamics differs slightly from its HBr counterpart.

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“…The Doppler-free two-photon excitation of the 6S 1/2 state by the two counter-propagating beams causes the atoms to see always a frequency of ω L1 + ω L2 = ω + ω − (k L1 − k L2 )V = 2ω for k L1 = k L2 , independent of their velocity V [10]. This is true when one photon comes from one beam and the second from the other.…”

Section: Resultsmentioning

confidence: 99%

Fabrication of 70-nm-Pitch Two-Level Interconnects by using Extreme Ultraviolet Lithography

Nakamura¹,

Oda²,

Soda³

et al. 2011

Jpn. J. Appl. Phys.

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We investigate the emissions of atomic potassium excited by two photons near the 4S 1/2 -6S 1/2 transition. Radiation near the 6S 1/2 -4P 3/2,1/2 and 4P 3/2,1/2 -4S 1/2 transitions are studied for the unidirectional and the bidirectional cases, respectively. It is shown that the total output intensity increases considerably for the bidirectional propagation. This is attributed to the effective increase of the Doppler free excitation and the cancellation of the quantum interference effect that is associated with the multiple paths of excitation of certain states.

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Doppler-free multi-photon ionization: a proposal for enhancing ion images

Cited by 21 publications

References 19 publications

Differential cross section for the H+D2→HD(v′=1,j′=2,6,10)+D reaction as a function of collision energy

Differential cross section for the H+D2→HD(v′=1,j′=2,6,10)+D reaction as a function of collision energy

Construction and calibration of an instrument for three-dimensional ion imaging

Fabrication of 70-nm-Pitch Two-Level Interconnects by using Extreme Ultraviolet Lithography

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