Preferential energization of lower‐charge‐state heavier ions in the near‐Earth magnetotail

Both A + T-rich oligonucleotides with and without self-complementary sequences were analyzed using ion-pair reversed-phase liquid chromatography/electrospray ionization mass spectrometry (IP-RP-HPLC/ESI-MS) by tryethylammonium acetate (TEAA) and hexafluoroisopropanol (HFIP) buffer systems to study the characteristics of their retention behavior and electrospray ionization tandem mass spectrometry (ESI-MS/MS) response. The results indicated that the chain length had the same effect on the retention of A + T-rich oligonucleotides in both of TEAA and HFIP buffer systems but the sequence had a different impact on the retention in the two buffer systems. A + T-rich oligonucleotides with a self-complementary sequence were much shorter than those without in the TEAA buffer system whereas a slight difference was observed in the HFIP buffer system. Similar total ion current (TIC) intensity was observed both in oligonucleotides with or without self-complementary sequence. The opposite trend of a change in the TIC intensities with increasing chain length were observed in both the TEAA and HFIP buffer systems. A lower charge state was predominant in the TEAA buffer system whereas a higher charge state was mainly distributed in the HFIP buffer system. The oligonucleotides without self-complementary sequences had a higher charge state than those with self-complementary sequences. A- and T- are more esily formed at a higher charge state whereas the sequence fragments will be formed more easily at a lower charge state in both A + T-rich oligonucleotides with and without self-complementary sequences.

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Dependence of silicon ablation regimes on fluence during ultrafast laser irradiation

Laser and Particle Beams ◽

10.1017/s0263034615001044 ◽

2016 ◽

Vol 34 (1) ◽

pp. 143-150 ◽

Cited By ~ 5

Author(s):

M. Polek ◽

A. Hassanein

Keyword(s):

Charge State ◽

Laser Energy ◽

Bubble Formation ◽

Femtosecond Laser Ablation ◽

Small Variation ◽

Ion Flux ◽

Average Charge ◽

Layer Depth ◽

Average Charge State ◽

Lower Charge

AbstractModels and experiments were developed to study femtosecond laser ablation of silicon using 800 nm, 40 fs pulses with fluences ranging from 0.5 to 35 J/cm2. At low fluences, ablation was found to occur due to bubble formation and splashing within the melt layer. At higher fluences, it was found that the ablation depth exceeded the melt layer depth due to shockwave ablation. The variation in ion flux and ion velocity was also studied both experimentally and theoretically. It was found that the variation in ion flux is mainly dependent on the variation in the average charge state, with only a small variation in the total number of ions above $\sim \!\!1.5\; \,{\rm J/c}{{\rm m}^2}$. Comparisons between the theoretical and experimental ion flux showed that higher charge state ions received greater portion of the laser energy compared with lower charge state ions.

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