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The dependence of multiply charged ions on laser ellipticity in methyl iodide clusters with 532 nm nanosecond laser was measured using a time-of-flight mass spectrometer. The intensities of multiply charged ions Iq+(q= 2–4) with circularly polarised laser pulse were clearly higher than those with linearly polarised laser pulse but the intensity of single charged ions I+was inverse. And the dependences of ions on the optical polarisation state were investigated and a flower petal and square distribution for single charged ions (I+, C+) and multiply charged ions (I2+, I3+, I4+, C2+) were observed, respectively. A theoretical calculation was also proposed to simulate the distributions of ions and theoretical results fitted well with the experimental ones. It indicated that the high multiphoton ionisation probability in the initial stage would result in the disintegration of big clusters into small ones and suppress the production of multiply charged ions. [ABSTRACT FROM AUTHOR]

Abstract: As efforts continue to elucidate laser–cluster interactions, we investigated the influence of laser wavelength on ion products. In this study, a pulsed methyl iodide cluster was irradiated with a Nd–YAG nanosecond laser, and the ion products were analyzed using time-of-flight mass spectrometry. Multiple-charge atomic ions of C q+ and I q+(q ⩾2) were observed using 532 and 1064nm laser wavelengths; however, only single-charge atomic and molecular ions appeared at 266 and 355nm. We show that the charge-state distribution for multiple-charge ions is almost independent of laser intensity. A three-stage model was developed to further understand these experimental results: the inverse electron bremsstrahlung heating rate is proportional to the square of laser wavelength, which seems to explain the dependence of multiple-charge ions on the wavelength. [Copyright &y& Elsevier]

This paper investigated the dependence of multiply charged ions on the laser polarization state when benzene cluster was irradiated with 532 and 1064 nm nanosecond laser. A circle, square and flower distribution for C 2+ , C 3+ and C 4+ were observed with 532 nm laser respectively, while flower petals for C 2+ , C 3+ and C 4+ were observed at 1064 nm as the laser polarization varied. A theoretical calculation was performed to interpret the polarization state and wavelength dependence of the multiply charged ions. The simulated results agreed well with the experimental observation with considering the contribution from the cluster disintegration. [ABSTRACT FROM AUTHOR]

Abstract: The formation mechanism for multiply charged ions (C q + and O q + (q =2–4)) were investigated using a dual polarity time-of-flight mass spectrometer when diethyl ether clusters interacted with nanosecond laser pulse. The signal intensity of multiply charged ions and electron energy was measured experimentally. It was shown that the intensity of multiply charged ions increased about 50 times when laser intensity increased from 7.6×109 to 7.0×1010 W/cm2, then saturated as laser intensity increased further. It is interesting that the evolution of the mean value of electron energy was same to that of multiply charged ions. The theoretical calculation showed the ionization potential of atomic ions could be significantly decreased due to the effect of Coulomb screening especially at low laser intensity. It indicated that the electron ionization combined with Coulomb screening effect could explain the production of multiply charged ions in nanosecond laser field. [ABSTRACT FROM AUTHOR]