Decomposition of the TOF spectrum into four Lorentzian curves: <sup>20</sup>Ne<sup>+</sup> from the uncondensed gas and from the cluster, and <sup>22</sup>Ne<sup>+</sup> from the uncondensed gas and from the cluster

<p><strong>Figure 2.</strong> Decomposition of the TOF spectrum into four Lorentzian curves: <sup>20</sup>Ne<sup>+</sup> from the uncondensed gas and from the cluster, and <sup>22</sup>Ne<sup>+</sup> from the uncondensed gas and from the cluster.</p> <p><strong>Abstract</strong></p> <p>We carried out time-of-flight mass spectrometry for neon clusters that were exposed to intense free electron laser pulses with the wavelength of 62 nm, which induce optical transition from the ground state (2s<sup>2</sup> 2p<sup>6</sup>) to an excited state (2s<sup>2</sup> 2p<sup>5</sup><em>nl</em> ) in the Ne atoms. In contrast to Ne<sup>+</sup> ions produced by two-photon absorption from isolated Ne atoms, the Ne<sup>+</sup> ion yield from Ne clusters shows a linear dependence on the laser intensity (<em>I</em>). We discuss the ionization mechanisms which give the linear behaviour with respect to <em>I</em> and expected features in the electron emission spectrum.</p>