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Tran S, Tran KC, Saenz Rodriguez A, Kong W. Kinetic energy distributions of atomic ions from disintegration of argon containing nanoclusters in moderately intense nanosecond laser fields: Coulomb explosion or hydrodynamic expansion. Phys Chem Chem Phys 2024; 26:8631-8640. [PMID: 38436420 DOI: 10.1039/d3cp05894h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
We report kinetic energies (KE) of multiply charged atomic ions (MCAI) from interactions of moderately intense nanosecond lasers at 532 nm with argon containing clusters, including neat and doped clusters with a trace amount of trichlorobenzene. We develop a mathematical method to retrieve speed and thereby kinetic energy information from analyzing the time-of-flight profiles of the MCAI. This method should be generally applicable in detections of energetic charged particles with high velocities, a realm where velocity map imaging is inadequate. From this analysis, we discover that the KE of MCAI from doped clusters demonstrates a quadratic dependence on the charge of the atomic ions, while for neat clusters, the dependence is cubic. This result confirms the nature of the cluster disintegration process to be dominated by Coulomb explosion. This result bears more similarity to reports from extreme vacuum ultraviolet (EUV) fields with similar intensities, than to reports from near infrared (NIR) intense laser fields. However, the charge state distribution from our experiment is the opposite: we observe more higher charge state ions than reported in EUV fields, and our charge state distribution is actually similar to those reported in NIR fields. We also report a significant effect of the external electric field on the charge state distribution of the atomic ions: the presence of an electric field can significantly increase the charge from the atomic ions, as shown by a three-fold reduction in the average kinetic energy per charge. Although molecular dynamics simulations have been implemented for experiments in the EUV and NIR, our results allude to the need of a concerted effort in this regime of moderately intense nanosecond laser fields. The significant decrease in charge state distribution and the significant increase in KE from doped clusters, compared with neat clusters, is a telltale sign that the true interaction time between the laser field and the cluster may be substantially shorter than the duration of the laser, a welcome relief for molecular dynamics simulations.
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Affiliation(s)
- Steven Tran
- Department of Chemistry, Oregon State University, Corvallis, Oregon, 97331, USA.
| | - Kim C Tran
- Department of Chemistry, Oregon State University, Corvallis, Oregon, 97331, USA.
| | - Axel Saenz Rodriguez
- Department of Mathematics, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon, 97331, USA.
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The scaling law of cluster sizes revisited: clusters formed via coexpansion of a molecular and a rare gas species. Chem Phys Lett 2023. [DOI: 10.1016/j.cplett.2023.140312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Yao Y, Zhang J, Kong W. Effects of aromatic molecules inside argon clusters on the formation of multiply charged atomic ions in moderately intense nanosecond laser fields. J Chem Phys 2022; 157:044307. [DOI: 10.1063/5.0096594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the effect of two molecular species, fluorene (C13H10) and 1, 3, 5-trichlorobenzene (C6H3Cl3, 3ClB), embedded in atomic argon clusters, on the generation of multiply charged atomic ions (MCAI) in moderately intense nanosecond laser fields at 532 nm. The near resonant-enhancement of two photon absorption in the two aromatic species produces only a few low charge state (+2) atomic ions in a neat molecular cluster, but enclosure of the same cluster with layers of Ar can significantly increase the charge state of MCAI. The yields of singly charged atomic ions from the molecular species, such as H+, C+, and Cl+, are positively correlated to the number of molecules inside an Ar cluster, but the yields of the MCAI and Ar+ demonstrate opposite behaviors. A higher number of aromatic molecules is actually detrimental to the production of Ar+ and of MCAI. Results of exponential fittings of the yields of MCAI at different laser intensities reveal a systematic change for the exponent of Ar+: with increasing concentrations of 3ClB in Ar clusters, the exponent decreases and eventually reaches the same value as those of MCAI. These results are consistent with our previous hypothesis that the formation mechanism of MCAI may be different from that of singly charged species, and that the strong resonance of Ar3+ may play an important role in the overall energy absorption. Moreover, the effect of the molecular core seems to change the formation mechanism of Ar+ to that of MCAI.
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Affiliation(s)
- Yuzhong Yao
- Oregon State University, United States of America
| | - Jie Zhang
- Chemistry, Oregon State University, United States of America
| | - Wei Kong
- Chemistry, Oregon State University, United States of America
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Yao Y, Zhang J, Pandey R, Wu D, Kong W, Xue L. Intensity dependence of multiply charged atomic ions from argon clusters in moderate nanosecond laser fields. J Chem Phys 2021; 155:144301. [PMID: 34654315 DOI: 10.1063/5.0065086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We report the laser intensity dependence of multiply charged atomic ions (MCAIs) Arn+ with 2 ≤ n ≤ 8 from argon clusters in focused nanosecond laser fields at 532 nm. The laser field, in the range of 1011-1012 W/cm2, is insufficient for optical field ionization but is adequate for multiphoton ionization. The MCAI sections of the mass spectra for clusters containing 3700 and 26 000 atoms are dominated by Arn+ with 7 ≤ n ≤ 9, extending to Ar14+. While the distributions of the MCAIs remain largely constant throughout the intensity range of the laser, the abundance of Ar+ relative to the abundances of the MCAIs increases dramatically with increasing laser intensity. Consequently, exponential fittings of the yields result in a larger exponent for Ar+ than for MCAIs, and the exponents of MCAIs with 2 ≤ n ≤ 8 are similar, with only slight variations for different charge states. The width of the arrival time and, hence, the corresponding kinetic energy of Ar+ also increases with increasing laser intensities, while the width of the arrival time of MCAIs remains constant throughout the range of measurements. These results call for more detailed theoretical investigations in this regime of laser-matter interactions.
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Affiliation(s)
- Yuzhong Yao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Rahul Pandey
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Di Wu
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Lan Xue
- Department of Statistics, Oregon State University, Corvallis, Oregon 97331, USA
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Yao Y, Freund WM, Zhang J, Kong W. Volume averaging effect in nonlinear processes of focused laser fields. J Chem Phys 2021; 155:064202. [PMID: 34391368 DOI: 10.1063/5.0061038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We report theoretical derivations and experimental results on the volume averaging effect of nonlinear processes in focused laser fields. This effect is considered detrimental in revealing the intensity dependence of a nonlinear process, caused by the intensity variation across the sampled volume of a focused laser. Following the treatment in the literature, we prove that if the signal dependence can be expressed as a simple power function of the laser intensity and if the detection region encompasses effectively the whole volume, volume average does not affect the final conclusion on the derived exponent. However, to reveal the detailed saturation effect of a multi-photon process, intensity selective scans involving spatial filters and displacement of the laser focus (z-scan) are required. Moreover, to fully capture the dependence of the signal on the variation of the laser intensity, the degree of spatial discrimination and the corresponding range of the z-scan need to be modeled carefully. Limitations in the dynamic range of the detector or the laser power, however, can thwart the desired scan range, resulting in erroneous fitting exponents. Using our nanosecond laser with a non-ideal Gaussian beam profile based on multiphoton ionization of argon atoms from a collimated molecular beam and from ambient argon gas, we report experimental measurements of the beam waist and Rayleigh range and compare the experimental intensity dependence of Ar+ with theoretical values. Agreements between theory and experiment are remarkable.
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Affiliation(s)
- Yuzhong Yao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
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Das S, Sharma P, Singh R, Vatsa RK, Tripathi VK. Multiple ionisation and Coulomb explosion in terawatt photoexcitation of Xenon clusters: An experimental and theoretical study. J Photochem Photobiol A Chem 2021. [DOI: 10.1016/j.jphotochem.2020.112884] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Yao Y, Zhang J, Pandey R, Kong W. Production of Multiply Charged Argon Ions in Moderate Nanosecond Laser Fields: An Open Question or a Forgone Conclusion? J Phys Chem Lett 2020; 11:9971-9974. [PMID: 33207881 PMCID: PMC8009038 DOI: 10.1021/acs.jpclett.0c02948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We reply to the Viewpoint by Vatsa and Mathur on our publication reporting the observation of multiply charged atomic ions from argon clusters doped with aromatic chromophores in a moderate nanosecond laser field. Vatsa and Mathur raised three concerns about the proposed explanation and offered additional ideas for the reported process. We agree with some of their concerns and welcome the addition of information, and we also clarify a few misunderstandings of our intention, perhaps caused by our implicit assumption of contextual relations. While the experimental results are indisputable, the interpretation is still a topic of debate, subject to further experimental investigations and theoretical modeling.
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Affiliation(s)
- Yuzhong Yao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Rahul Pandey
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
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Vatsa RK, Mathur D. Generation of Multiply Charged Argon Ions in Nanosecond Laser Field Ionization of Argon Clusters. J Phys Chem Lett 2020; 11:9842-9845. [PMID: 33207882 DOI: 10.1021/acs.jpclett.0c02223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Zhang and co-workers ( J. Phys. Chem. Lett. 2020, 11, 1100-1105) have recently reported results of experiments involving irradiation of argon clusters doped with bromofluorene chromophores by nanosecond-long pulses of 532 nm laser light. Multiply charged ions of atomic argon (Arn+, 1 ≤ n ≤ 7) and carbon (Cn+, 1 ≤ n ≤ 4) are observed, which are sought to be rationalized using an evaporation model. The distinguishing facet of exploding clusters being progenitors of energetic ions and electrons constitutes the key driver for contemporary research in laser-cluster interactions; it is, therefore, important to point out inconsistencies that are intrinsic to the model of Zhang and co-workers. In light of similar reports already in the literature, we show that their model is of limited utility in describing the dynamics that govern how fast, multiply charged atomic ions result from laser irradiation of gas-phase clusters. We posit that it is plasma behavior that underpins cluster heating and cluster explosion dynamics.
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Affiliation(s)
- Rajesh K Vatsa
- Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Deepak Mathur
- Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal 576 104, India
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