Anisotropic Coulomb explosion of acetylene and diacetylene derivatives

Abstract

We investigated the significant differences in the angular distribution of carbon ions ejected from dimethylacetylenes (CH 3-C≡C-CH 3 and CH 3-C≡C-C≡C-CH 3) and diiodoacetylenes (I-C≡C-I and I-C≡C-C≡C-I) induced by a Coulomb explosion. The longest linear chain molecule ever reported was exposed to intense femtosecond laser fields (40 fs, < 5×10 14 Wcm-2) in this study. In the cases of the diiodoacetylenes, the angular distributions of the carbon ions were orthogonal with respect to the laser polarization direction and became narrower as the length of the molecules became longer. This is in sharp contrast to the dimethylacetylenes, in which the angular distributions of the carbon ions were parallel with respect to the laser polarization direction and became broader as the length of the molecules became longer. The specific angular distributions of carbon ions ejected from the diiodoacetylenes are explained in terms of the frozen molecular rotation, the blocking of carbon ion emission, and the bending of carbon chains at highly charged states due to the presence of iodines.

Intact Four‐atom Organic Tetracation Stabilized by Charge Localization in the Gas Phase

“…Therefore, CI 2 + ,i fi t exists, appears as ad ouble peak owing to its certaink inetic [ energy. [18] Furthermore, as ingle peak appeared at m/z = 69.75 ( Figure S2) was assigned to the isotope peak of DIA 4 + ( 12 C 13 CI 2 4 + )b ased on its position as well as intensity relative to that of dominant peak ( 12 C 2 I 2 4 + ). The resolutions of the peaks (m/Dm,f whm) were 930 (DIA + ), 1.15 10 3 (DIA 2 + ), 1.37 10 3 (DIA 3 + ), and 1.58 10 3 (DIA 4 + ).…”

“…According to our density functional theory (DFT) calculations, the stabilityo ft he surprisingly small DIA tetracation is explained in terms of the dominant (91-95 %) localization of the positive charges on the terminal iodine atoms;i ns uch ac ondition, Coulombic repulsions between iodine and carbon atoms (and between carbon atoms) in the DIA tetracation are minimized.Intact tri-and tetracations of DIA and DIDA were generated in abundance (Figures 1a,b, S1 and S2) in femtosecondl aser fields (0.8 mm, 45 fs, > 10 14 Wcm À2 ). Some atomic ions such as iodines and carbons were observed but they did not originate from MMCs( 4 +)b ut from more highly chargeds tates [18] judgingf rom their kinetice nergy estimated by the peak splitting. MMCs were definitively identifiedb yt he mass-to-charge ratio (m/z), isotope pattern, and narrower peak width than those of lower-charged ions.…”

“…Intact tri-and tetracations of DIA and DIDA were generated in abundance (Figures 1a,b, S1 and S2) in femtosecondl aser fields (0.8 mm, 45 fs, > 10 14 Wcm À2 ). Some atomic ions such as iodines and carbons were observed but they did not originate from MMCs( 4 +)b ut from more highly chargeds tates [18] judgingf rom their kinetice nergy estimated by the peak splitting. MMCs were definitively identifiedb yt he mass-to-charge ratio (m/z), isotope pattern, and narrower peak width than those of lower-charged ions.…”

“…The heavy mass effects on the prompt Coulombe xplosion of DIA and DIDA has been investigated under such conditions. [18] Although the amount of charge is smaller,t he appearance of the tetracation of such as mall p-moiety is stills urprising, and cannot be explained as in the case of large aromatic hydrocarbons. According to our density functional theory (DFT) calculations, the stabilityo ft he surprisingly small DIA tetracation is explained in terms of the dominant (91-95 %) localization of the positive charges on the terminal iodine atoms;i ns uch ac ondition, Coulombic repulsions between iodine and carbon atoms (and between carbon atoms) in the DIA tetracation are minimized.Intact tri-and tetracations of DIA and DIDA were generated in abundance (Figures 1a,b, S1 and S2) in femtosecondl aser fields (0.8 mm, 45 fs, > 10 14 Wcm À2 ).…”

“…We conclude that the persistence of terminal iodine atoms in close proximity to carbon framework, even in the MMCs of DIA and DIDA, results in the formationo ft hese fragment ions. [18] The persistence of chemical bond for electron removal depends on the charactero fm olecular orbitals where electrons are ejected. The first electron was considered to be removed from the highest occupied molecular orbital( HOMO) because the angular distribution of the electron stripped from small molecules via tunneling was strongly correlated with the shape of the HOMO.…”