Molecular symmetry effects in the ionization of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>CS</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>by intense few-cycle laser pulses

Mathur, D.; Dharmadhikari, A. K.; Rajgara, F. A.; Dharmadhikari, J. A.

doi:10.1103/physreva.78.013405

Cited by 23 publications

(9 citation statements)

References 31 publications

(27 reference statements)

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“…This implies that CO + (1,0) production strongly dominates the predissociation mechanism in the strong field regime, whilst this feature is mostly independent of driving laser intensity and wavelength. The obtained branching ratio is very similar to particle collision-excitation experiments [131] ) preferentially causing vibrational excitation. With only pathway 7.3 remaining and requiring a bent configuration of the molecular ion, one may conclude that CO + 2 is mostly formed in the linear configuration with only a small amount of ions being present in the bent configuration.…”

Section: Discussionsupporting

confidence: 70%

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Resolving Strong Field Dynamics in Cation States of CO_2 via Optimised Molecular Alignment

Oppermann

2014

Springer Theses

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In this thesis, the role of the molecular structure in strong field induced processes in CO 2 is resolved by the use of optimised impulsive molecular alignment. Two processes were investigated: recollision induced ionisation and the dissociation of the molecular ion CO + 2 . Both processes are driven by the initial tunneling ionisation of CO 2 . Through the use of molecular alignment, the orbital symmetries of the involved molecular ionic states were resolved, revealing the internal molecular dynamics in the form of ionisation and excitation pathways.A novel data analysis procedure was developed to extract the alignment distribution and rotational temperature of the impulsively aligned molecular ensemble. This facilitated the optimisation of molecular alignment in mixed gas samples and was demonstrated for N 2 , O 2 and CO 2 seeded in Ar.The recollision induced or nonsequential double ionisation (NSDI) of CO 2 was then studied in the molecular frame. The process was fully characterised by measuring the shape of the recolliding electron wavepacket and the angularly resolved inelastic electronion recollision cross section. The results reveal the contribution from both the ionic ground and first excited state of CO + 2 to the NSDI mechanism. This study was extended to the strong field induced dissociation of impulsively aligned CO + 2 . It was found that dissociation is driven by a parallel dipole transition from the second excited ionic state B to the predissociating state C, whilst recollision excitation was shown to not play a role. The strong field induced coupling of the ionic states B and C could thus be controlled by the laser polarisation.The results obtained in this thesis further the understanding of population dynamics of cation states in strong field processes. This is of special interest for extending molecular strong field physics to the study of electronic degrees of freedom and their coupling to the nuclear motion. had hoped for in a research degree and I cannot thank Jon enough for making it such an enriching experience, both professionally and personally.

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Section: Discussionsupporting

confidence: 70%

“…Due to the large number of broad nodal planes in the HOMO of C6H6, this effect is expected to be visible even in a randomly oriented sample. A similar explanation has been used to explain the absence of recollision induced effects in CS 2 [131].…”

Section: Large Moleculesmentioning

confidence: 98%

Resolving Strong Field Dynamics in Cation States of CO_2 via Optimised Molecular Alignment

Oppermann

2014

Springer Theses

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“…An alternate method based on filamentation in rare gases has also found recent utility [4], and pulses as short as 5 fs have been generated by using two-stage filamentation in argon gas. This is the strategy that has been adopted in our laboratory [5] to generate few-cycle pulses of intense 800-nm light, which have been used by us to probe the ionization and fragmentation dynamics of molecules [6] and to demonstrate a unimolecular bond rearrangement in H 2 O on the time scale of a single vibrational period [7]. We now report application of such few-cycle pulses to studies of the strong-field dynamics of gasphase clusters of Ar.…”

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confidence: 99%

Strong-field ionization and Coulomb explosion of argon clusters by few-cycle laser pulses

et al. 2010

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Energy distributions are measured for ions emitted upon Coulomb explosion of Ar n clusters (n = 400-900) upon irradiation by intense three-cycle pulses (10 fs) of 800-nm laser light of peak intensity 5 × 10 14 W cm −2 . With few-cycle pulses, there is insufficient time for the cluster to undergo expansion; this results in overall dynamics that are significantly different from those in the many-cycle regime. The peak ion energies are much lower than those obtained when 100-fs pulses of the same intensity are used; they are almost independent of the size of the cluster (over the range 400-900 atoms). Ion yields are measured to be larger in the direction that is perpendicular to the laser-polarization vector than along it. Model molecular dynamics calculations are used to qualitatively rationalize this unexpected anisotropy in terms of shielding by a spatially asymmetric electronic-charge cloud within the cluster.

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“…Before discussing the LAES effect in detail, let us consider the possible contributions of other processes that occur in a strong laser field. As demonstrated in [22], ionization of the laser-dissociated fraction of water molecules has a low yield under the short-pulse condition. The laser pulse duration applied in the present study is comparable to the pulse duration used in [22].…”

Section: Resultsmentioning

confidence: 99%

“…As demonstrated in [22], ionization of the laser-dissociated fraction of water molecules has a low yield under the short-pulse condition. The laser pulse duration applied in the present study is comparable to the pulse duration used in [22]. Therefore, we neglect the contribution of the dissociation process.…”

Section: Resultsmentioning

confidence: 99%

Laser-assisted electron scattering in strong-field ionization of dense water vapor by ultrashort laser pulses

et al. 2014

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We report on strong-field ionization of dense water gas in a short infrared laser pulse. By employing a unique combination of photoelectron spectroscopy with a liquid micro-jet technique, we observe how the character of electron emission at high kinetic energies changes with the increase of the medium density. This change is associated with the process of laser-assisted electron scattering (LAES) on neighboring particles, which becomes a dominant mechanism of hot electron emission at higher medium densities. The manifestation of this mechanism is found to require densities that are orders of magnitude lower than those considered for heating the laser-generated plasmas via the LAES process. The experimental results are supported by simulations of the LAES yield with the use of the Kroll-Watson theory.

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Molecular symmetry effects in the ionization ofCS2by intense few-cycle laser pulses

Cited by 23 publications

References 31 publications

Resolving Strong Field Dynamics in Cation States of CO_2 via Optimised Molecular Alignment

Resolving Strong Field Dynamics in Cation States of CO_2 via Optimised Molecular Alignment

Strong-field ionization and Coulomb explosion of argon clusters by few-cycle laser pulses

Laser-assisted electron scattering in strong-field ionization of dense water vapor by ultrashort laser pulses

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