Low-power resonant laser ablation of copper

Gill, Chris G.; Allen, Todd M.; Anderson, Jason; Taylor, T.N.; Kelly, Peter B.; Nogar, N. S.

doi:10.1364/ao.35.002069

Cited by 23 publications

(30 citation statements)

References 58 publications

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“…For the proposed experiment the laser irradiance amounts to only 2 · 10 5 Wcm −2 and is therefore three orders of magnitude below the typical laser ablation threshold for metals [31]. Nevertheless a minor desorption of surface atoms may still occur below the ablation threshold [32], leading to a reduction of irradiated thorium atoms after several 10 4 laser pulses. Such effects could be compensated for by using a moving (e.g.…”

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confidence: 92%

A Laser Excitation Scheme for Th229m

et al. 2017

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Direct laser excitation of the lowest known nuclear excited state in 229 Th has been a longstanding objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer's excitation energy compared to the presently adopted value of (7.8 ± 0.5) eV. Here we present a direct laser excitation scheme for 229m Th, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than 10 4 and a total measurement time of less than three days for laser scanning appear to be achievable.Direct nuclear laser excitation has come closer into reach within the past years, partly due to the development of free-electron-laser technology. Such ideas are typically dealing with the excitation of nuclear states in the energy range of at least a few keV or above [1,2]. However, there is one exceptional nuclear state known for the last 40 years with a significantly lower energy of presumably below 10 eV [3,4]. An excitation energy of (7.8 ± 0.5) eV, corresponding to (159 ± 11) nm wavelength or ∼ 1900 THz, is by today the most accepted value for the isomeric first excited state of 229 Th [5,6]. This state conceptionally allows for direct nuclear laser excitation using solid-state laser technology and was proposed for the development of a nuclear clock of extremely high stability, due to an expected high resilience against external influences and a radiative lifetime in the range of minutes to hours [7][8][9][10]. It is generally assumed that direct nuclear laser excitation of 229m Th requires a considerably improved knowledge of the isomeric transition energy (see e.g. Ref.[11] and references therein). The reasons are that, first, the present uncertainty in the knowledge of the isomeric energy value is still rather large. The currently best energy value of 7.8±0.5 eV leads to an energy range of at least 1 eV (corresponding to 2.4·1014 Hz) to be scanned when searching for the isomeric excitation. Second, the radiative lifetime of 229m Th was theoretically predicted to be in the range of hours [12][13][14], leading to long required detection times when searching for a radiative decay channel. This has led to the assumption that the required time for laserbased scanning of the large energy range of 1 eV would be prohibitively long. In order to shorten the required scanning times, there are worldwide efforts ongoing to decrease the uncertainty of the transition energy, which would bring the isomeric state into realistic reach of direct laser excitation (see e.g. Refs. [15-18]). A recent review is found in Ref. [11].Here we propose a different approach, which allows for a direct laser excitation of 229m Th without the requirement of an improved knowledge of the transition energy. As the requi...

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confidence: 92%

A Laser Excitation Scheme for Th229m

et al. 2017

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“…It has been observed by this and other research groups 21,23,24 that the ion signal obtained by resonant laser ablation has a higher order (n > 5) dependence upon the laser pulse intensity used when compared with non-specific laser ablation ionization, which has a pulse energy dependence of 1 < n < 3. Figure 6 shows the laser pulse energy dependence for RLA of copper in a 304L stainless steel sample as measured by the quadrupole ion trap mass spectrometer.…”

Section: Induced Rf-depression Experimentsmentioning

confidence: 57%

“…The dye laser had a ≤ 0.2 cm -1 bandwidth, and a ~12 ns pulse duration. For these experiments the dye laser output was tuned to 463.507 nm, corresponding to the copper '2 + 1' resonant ionization scheme (photons to resonance + photons to ionize) described in previous work 11,21 with the resonant level excited corresponding to the [Ar](3d 10 5s) 2 S 1/2 level of Cu(I). Precise laser pulse energy control was achieved for these experiments by using a variable laser attenuator (NRC, #935-5) in the beam line, near the vacuum interface.…”

Section: Methodsmentioning

confidence: 99%

“…A selective ionization scheme is one way to reduce space-charge problems from bulk matrix ions and eliminate the disruption of the ion trapping fields during the ionization event. Resonant laser ablation (RLA), [16][17][18][19][20][21] allows both for analyte selectivity from a multicomponent sample and laser ionization using very low fluences when the generation of atomic ions is required, say for elemental analysis or for chemical ionization reagent ions. A more general route would also be to use a selective ion injection method, but this may be an unnecessarily complicated technique for laser desorption or ablation experiments.…”

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confidence: 99%

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Laser Ablation Ion Trap Mass Spectrometry—Storage Field Suppression and its Effect Upon Analytical Performance

Gill

Garrett

Nogar

et al. 1997

Rapid Commun. Mass Spectrom.

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The combination of laser desorption and ablation with mass spectrometry has been, and will continue to be, a useful marriage of technologies. Quadrupole ion trap mass spectrometry, which has evolved from a simple mass selective detector for gas chromatography to a high performance analytical tool over the last decade, is being coupled more frequently with desorption sources, such as lasers and particle beams. The present work addresses a shortcoming of the use of laser sampling with quadrupole ion traps: laser ablation of samples directly within the storage volume of the trap can lead to suppression of the RF storage field, thereby reducing ion-trapping efficiency during the ionization event. A systematic examination of the phenomenon has been conducted and the advantages of selective injection or ionization methods, such as resonant laser ablation, for elimination of this problem are presented.

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“…RLA of different metallic materials has been investigated by nanosecond pulses from Nd:YAG-pumped dye lasers [7][8][9][10][11] or excimer-pumped dye lasers [12]. RLA of polymers by picosecond pulses from freeelectron lasers has also been studied [13,14].…”

Section: Introductionmentioning

confidence: 99%

Resonant effects in nonlinear photon absorption during femtosecond laser ablation of Nd-doped silicate glass

et al. 2012

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This study investigates the resonant effects in nonlinear photon absorption in femtosecond laser ablation of Nd-doped silicate glass (Nd:glass). During the femtosecond laser ablation process, the resonant ablation threshold fluence is decreased by up to 40% compared with that of ordinary ablation. However, it is found that the resonant effect is closely related with laser intensity, and lower laser intensities are required to achieve a significant enhancement. When the intensity is lower than 2.28×10(14) W/cm(2) at which multiphoton ionization dominates, resonant effect is enhanced by a factor of 1.4 to 4.4. When the intensity is higher than 2.28×10(14) W/cm(2), at which intensity tunnel ionization dominates, the resonant effect becomes weak and gradually fades away. It is shown that the resonant effect is still important for multiphoton ionization yet insignificant for tunnel ionization.

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Low-power resonant laser ablation of copper

Cited by 23 publications

References 58 publications

A Laser Excitation Scheme for Th229m

A Laser Excitation Scheme for Th229m

Laser Ablation Ion Trap Mass Spectrometry—Storage Field Suppression and its Effect Upon Analytical Performance

Resonant effects in nonlinear photon absorption during femtosecond laser ablation of Nd-doped silicate glass

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