Ionization of Linear Alcohols by Strong Optical Fields

Abstract

We have experimentally probed the strong-field ionization dynamics of gas-phase linear alcohols, methanol, ethanol, and 1-propanol, by irradiating them with intense, femtosecond-duration laser pulses of 800 and 400 nm wavelength. Specifically, we make high resolution measurements of the energies of electrons that are ionized by the action of the optical field. Our electron spectroscopy measurements enable us to bifurcate the dynamics into multiphoton ionization and tunneling ionization regimes. In the case of 800 nm irradiation, such bifurcation into different ionization regimes is reasonably rationalized within the framework of the adiabaticity parameter based on the original Keldysh-Faisal-Reiss model of atomic ionization, without recourse to any structure-dependent modifications to the theory. In that sense, our 800 nm spectroscopy indicates that the linear alcohols exhibit atom-like properties as far as strong field ionization dynamics in the multiphoton ionization and tunneling regimes are concerned. We also explore the limitations of this atom-like picture by making measurements with 400 nm photons wherein the ponderomotive potential experienced by the ionized electrons is much less than the photon energy; effects that are purely molecular then appear to influence the strong field dynamics.

Observation of Ultrafast Charge Migration in an Amino Acid

“…25 Therefore, it is more probable that the atomic-like n N orbital is ionized by the VIS/NIR pulse than the π 1 orbital. 26 The yield of immonium dications is a particularly sensitive probe of charge location because the local ionization potential will increase as the hole approaches the amine group causing ionization by the VIS/NIR pulse to be suppressed. It is worth noting that fluctuations in the data close to time zero visible in the inset of Figure 4 might be produced by charge oscillations to and from the amine site with a period close to the duration of the probe pulse (∼6 fs), although this needs to be confirmed by additional experiments with improved statistics.…”

Ultrafast strong-field dissociative ionization dynamics of CH2Br2 probed by femtosecond soft x-ray transient absorption spectroscopy

“…The dependence of the tunnel ionization rate on internuclear separation 21 enables the creation of a vibrational wavepacket in the electronic ground state of D 2 using few-cycle pulses. On the other hand, the atomiclike ionization behavior of polyatomics such as alcohols 26 and methyl halides 27 can be attributed to the localization on a single atom of the orbital that is ionized ͑typically the highest occupied molecular orbital͒. 23 For larger molecules, such as linear polyenes 24 and polycyclic aromatic hydrocarbons, 25 measuring their extent of fragmentation as a function of laser intensity and wavelength reveals the importance of nonadiabatic ionization and multielectron effects; these effects are attributed to the presence of spatially delocalized, low-lying electronically excited states in molecules with extensive -conjugation.…”

Experimental Retrieval of Target Structure Information from Laser-Induced Rescattered Photoelectron Momentum Distributions

“…Comparing the time origin of the TOF spectrometer from this calibration with the measured one, we estimated that the error of the energy scale in our data is <5%. The efficacy of our high resolution electron spectroscopy technique to study strong field molecular dynamics has been recently demonstrated [17][18][19]. Further details of the experimental setup and procedure are given elsewhere [20,21].…”