Kinetic energy distributions of ionic fragments produced by subpicosecond multiphoton ionization of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Boyer, K.; Luk, T. S.; Solem, J. C.; Rhodes, C. K.

doi:10.1103/physreva.39.1186

Cited by 135 publications

(63 citation statements)

References 21 publications

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“…Although the enhancement of the ionization at R c was understood, how the molecule reaches R c from its initial equilibrium separation remains unexplained. In addition, many experiments have provided evidence of asymmetric dissociation channels [6,[15][16][17][18][19] and these channels appear to be formed at smaller internuclear separations than the symmetric channel [15,20]. This suggests that the asymmetric channel is not necessarily formed from the symmetric channel.…”

Section: Introductionmentioning

confidence: 95%

A framework for understanding molecular ionization in strong laser fields

Menon

Nibarger

Gibson

2002

J. Phys. B: At. Mol. Opt. Phys.

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The aim of this paper is to examine the role of excited states and multi-electron interactions in molecular ionization by strong laser fields. We present new data on the ionization and dissociation of iodine molecules that reveal important aspects of the strong field-molecule interaction in the short pulse regime. Our data, along with previous studies, is inconsistent with the simplest and commonly accepted model of molecular ionization in a strong laser field and this has led us to examine closely the individual ionization steps. We have found that a molecule can ionize into several distinct configurations predominantly through multi-electron interactions and the abundance of such configurations is dependent on internuclear separation. The ionization appears to be dominated by pairs of states with gerade and ungerade symmetry, as they have a large dipole coupling and the transition is near resonant with the strong laser field. In a oneelectron molecule, this pair consists of the ground and first excited state whereas in a two-electron molecule this corresponds to the lowest lying pair of ionic states. In this paper, we propose a framework for organizing the numerous ionization pathways based on the electronic configuration of the initial charge state.

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Section: Introductionmentioning

confidence: 95%

A framework for understanding molecular ionization in strong laser fields

Menon

Nibarger

Gibson

2002

J. Phys. B: At. Mol. Opt. Phys.

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“…The work of Tzallas et al [17] provides further evidence that ring opening, induced by strong laser fields, is possible. It therefore seems reasonable to assume that the abovementioned channels are plausible candidates based on the split structure observed in the 70 and 80 m/z range, and the indication in the momentum scaled mass spectrum of NB that the high mass fragments have release momenta consistent with H A number of polarization dependent studies of molecular ionization in the tunnel regime indicate that the ion peak shape is dependent on the amount of geometric or dynamic alignment experienced by the molecule [9,10,12,[45][46][47][48][49][50][51][52]. They generally find suppression of ionization when the polarization is circular, and enhancements of ionization in cases where the polarization is linear, with the CE component emphasized when the laser polarization is collinear with the time-of-flight spectrometer axis.…”

mentioning

confidence: 99%

Femtosecond laser photoionization time-of-flight mass spectrometry of nitro-aromatic explosives and explosives related compounds

Mullen

Coggiola

Oser

2009

J. Am. Soc. Mass Spectrom.

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The ultrafast laser-induced photoionization and photodissociation processes of the nitroaromatic containing explosive and explosive related compounds (ERCs) nitrobenzene (NB), 1,3-dinitrobenzene (DNB), m-nitrotoluene (MNT), 2,4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT) have been investigated at three laser wavelengths and power densities using a time-of-flight mass spectrometer. Examination of the mass spectra of these compounds reveals the enhanced formation of the molecular ion [M ϩ ] when ultraviolet (332 nm) and visible (495 nm) light is used relative to infrared (795 nm) radiation. In addition, at 795 nm and a power density of 3.5 ϫ 10 14 W/cm 2 , the presence of a competition between multiphoton ionization (MPI) and Coulomb explosion (CE) channels is revealed by peak shape analysis, and is thought to be operative under these conditions for all of the molecules investigated. [5][6][7][8][9][10][11][12], and polyatomic aromatic organic molecules [13][14][15][16][17][18][19][20][21][22][23], has been the subject of intense investigation. These studies have focused on the fundamental interaction of the laser pulse with the atomic or molecular system, and have generally found a number of operative ionization and dissociation mechanisms present, which are sensitive to the laser wavelength and power density. In addition, a number of studies have also been dedicated to the investigation of the analytical usefulness of femtosecond laser ionization toward molecular specific detection. A prime example is the application to the ionization and detection of the explosives and explosives related compounds pioneered by . Their studies focused on an understanding of the mass spectra obtained using ultrafast laser pulses in conjunction with time-of-flight mass spectrometry, M ϩ ion formation, and specific molecular fragments that could be assigned to a particular precursor species. Of particular interest was the demonstration of isomer dependent mass spectra for the three isomers of nitrotoluene.The motivation to apply femtosecond laser ionization to the study of explosives and ERCs originated from previous laser ionization work, which found that nanosecond laser ionization in the ultraviolet led to extensive molecular fragmentation [31][32][33][34][35][36]. The extensive fragmentation was determined to be non-useful for species-specific identification, even though abundant NO ϩ ions were observed in the mass spectra [37]. The presence of NO ϩ in the mass spectra of these species naturally raised questions regarding its formation. Mechanistically, it was discovered that the dissociative lifetimes of the intermediate states involved in the ionization process were about a few hundred femtoseconds, and that this rapid dissociation led to the extensive fragmentation observed in the mass spectra. Further, the presence of NO ϩ in the mass spectra of these species was attributed to rapid dissociation of the parent molecule (RNO 2 ) producing the NO 2 fragment. The NO 2 molecule undergoes an additional photon absorptio...

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“…Since the applied intensities in these investigations were a factor of about 10 higher than ours the ion temperature in our experiment may still be below 1 eV. However, for molecules the situation is more complicated since additional ion heating may result from a "Coulomb explosion" [28,29]. More investigations of optical-field ionization, especially in molecules, are needed in order to clarify the role of the various physical mechanisms affecting the ion temperature.…”

Section: B Nitrogenmentioning

confidence: 98%

xuv spectra of optical-field-ionized plasmas

et al. 1995

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High-power Ti:sapphire laser pulses (150 mJ in 150 fs) were focused into a gas jet of He, N2, CQ2, 02, SF6, or Ar emitted from a pulsed nozzle. The xuv spectra that were generated are reported and analyzed. For all gases the spectra show strong lines corresponding to single-electron transitions. This indicates that the applied intensities of up to 5 X 10' %/cm' readily strip the atoms of all outer electrons, with three-body recombination populating excited levels of the next lower ionization stage. Simulations of the plasma evolution after the laser pulse were performed for helium and nitrogen. In the case of helium, good agreement with the experiment can be obtained for specific initial conditions. For nitrogen, mechanisms other than three-body recombination must be invoked to explain the experimental spectra. Gain measurements were made by comparing longitudinal and transverse spectra.

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Kinetic energy distributions of ionic fragments produced by subpicosecond multiphoton ionization ofN2

Cited by 135 publications

References 21 publications

A framework for understanding molecular ionization in strong laser fields

A framework for understanding molecular ionization in strong laser fields

Femtosecond laser photoionization time-of-flight mass spectrometry of nitro-aromatic explosives and explosives related compounds

xuv spectra of optical-field-ionized plasmas

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