Pulse width effect on the dissociation probability of CH4 + in the intense femtosecond laser field

Abstract

The laser pulse width effect on the dissociation probability of CH 4 + irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 × 10 13 W/cm 2 was used. The observed relative yield of the primary fragment ion CH 3 + increases with increasing pulse width and tends to saturate when the pulse width is longer than 120 fs. The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCT) calculation were applied to predicting the dissociation probability of CH 4 + . The calculated probability is corrected with the molecular orientation effect and the spatial distribution of laser intensity. The modified results show that the dissociation requires at least 23 fs and saturates with long pulse widths (≥100 fs). The result is approximately consistent with the experimental observation.

Experimental and Theoretical Investigation of High-Power Laser Ionization and Dissociation of Methane

“…Within the laserpulse temporal duration and spatial distribution, the potential surfaces can be modified by the laser electric field, and if the laser intensity is strong enough, it can induce the ion dissociation during the laser duration. This type of dissociation is usually referred to as FAD [19][20][21] and occurs in the femtosecond range. The second type of ion dissociation occurs outside the temporal and spatial influence of the femtosecond laser pulse.…”

“…For the case in which the laser duration was 8 fs, only the primarily fragmental CH 3 + ion was observed, in addition to the parent CH 4 + ion. When the laser duration was increased to 30 fs, CH 2 + and H + began to appear, and when the laser duration reached 110 fs, some doubly charged ions were also observed, in addition to the abundant singly charged ions. , The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCD) calculation were applied to predict the dissociation probability of CH 4 + . − The calculated probability was corrected with the molecular orientation effect and the spatial distribution of laser intensity. The modified results indicated that the dissociation would require at least 23 fs and was saturated with long pulse widths (∼100 fs).…”

“…When the laser duration was increased to 30 fs, CH 2 + and H + began to appear, and when the laser duration reached 110 fs, some doubly charged ions were also observed, in addition to the abundant singly charged ions. 19,20 The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCD) calculation were applied to predict the dissociation probability of CH 4 + . [19][20][21] The calculated probability was corrected with the molecular orientation effect and the spatial distribution of laser intensity.…”

“…19,20 The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCD) calculation were applied to predict the dissociation probability of CH 4 + . [19][20][21] The calculated probability was corrected with the molecular orientation effect and the spatial distribution of laser intensity.…”

Methane Decomposition Using Metal-Assisted Nanosecond Laser-Induced Plasma at Atmospheric Pressure

“…Furthermore, Wu et al 24 practically studied the fragmentation pattern of CH 4 due to femtosecond laser shots. Wang et al 25 investigated the methane dissociation using femtosecond laser shots at 800 nm using the laser fluence ∼10 14 W/cm 2 . Suzuki et al 26 demonstrated the formation of formaldehyde from photo-oxidation of methane over a molybdena-silica catalyst at ∼500 K using UV irradiation.…”