| 1. |
- Bernard, Jérôme, et al.
(författare)
-
Efficient radiative cooling of tetracene cations C18H12+ : absolute recurrent fluorescence rates as a function of internal energy
- 2023
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 25:15, s. 10726-10740
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured recurrent fluorescence (RF) cooling rates of internally hot tetracene cations, C18H12+, as functions of their storage times and internal energies in two different electrostatic ion-beam storage rings – the cryogenic ring DESIREE with a circumference of 8.6 meters in Stockholm and the much smaller room temperature ring Mini-Ring in Lyon, which has a circumference of 0.71 meters. The RF rates were measured to be as high as 150 to 1000 s−1 for internal energies in the 7 to 9.4 eV energy range, where we have probed the time evolution of the internal energy distribution with nanosecond laser pulses with a 1 kHz repetition rate. These RF rates are found to be significantly higher than those of previously investigated smaller PAHs such as e.g. anthracene and naphthalene, for which the lowest non-forbidden electronic excited state, the D2 state, is populated with a smaller probability by inverse internal conversion. Furthermore, the D2–D0 transition rate is smaller for these smaller molecules than for tetracene. The complementary features of the two storage rings allow for RF rate measurements in a broader internal energy range than has been possible before. The smaller sampling period of about 6 μs in Mini-Ring is ideal to study the cooling dynamics of the hotter ions that decay fast, whereas DESIREE with a sampling period of about 60 μs is better suited to study the colder ions that decay on longer timescales ranging up to hundreds of milliseconds. The excellent agreement between the two series of measurements in the region where they overlap demonstrates the complementarity of the two electrostatic ion-beam storage rings.
|
|
| 2. |
- Chen, Fuqiang, et al.
(författare)
-
Radiative cooling of cationic carbon clusters, CN+, N=8,10,13-16
- 2019
-
Ingår i: Physical Chemistry Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21, s. 1587-1596
-
Tidskriftsartikel (refereegranskat)abstract
- The radiative cooling of highly excited carbon cluster cations of sizes N = 8, 10, 13–16 has been studied in an electrostatic storage ring. The cooling rate constants vary with cluster size from a maximum at N = 8 of 2.6 × 104 s−1 and a minimum at N = 13 of 4.4 × 103 s−1. The high rates indicate that photon emission takes place from electronically excited ions, providing a strong stabilizing cooling of the molecules.
|
|
| 3. |
- Kono, Naoko, et al.
(författare)
-
Electronic and vibrational radiative cooling of the small carbon clusters C4− and C6−
- 2018
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 98:6
-
Tidskriftsartikel (refereegranskat)abstract
- Delayed electron detachment yields of C4− and C6− induced by photoexcitation in an electrostatic ion storage ring were measured as functions of excitation energies and laser firing times, allowing for a mapping of their radiative cooling in a wide energy range. The energy window concept and discrimination of one- and twophoton absorption are critical in understanding the obtained results. The experimentally obtained electronic and vibrational cooling rates were consistent with a simulation based on detailed-balance theory. The even-odd alternation of vibrational cooling rates, predicted from IR intensities, was also examined. We found that the larger anion cools faster, with no indication of an even-odd alternation.
|
|
| 4. |
- Stockett, Mark H., et al.
(författare)
-
Unimolecular fragmentation and radiative cooling of isolated PAH ions : A quantitative study
- 2020
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 153:15
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved spontaneous and laser-induced unimolecular fragmentation of perylene cations (C20H12+) has been measured on timescales up to 2 s in a cryogenic electrostatic ion beam storage ring. We elaborate a quantitative model, which includes fragmentation in competition with radiative cooling via both vibrational and electronic (recurrent fluorescence) de-excitation. Excellent agreement with experimental results is found when sequential fragmentation of daughter ions co-stored with the parent perylene ions is included in the model. Based on the comparison of the model to experiment, we constrain the oscillator strength of the D-1 -> D-0 emissive electronic transition in perylene (f(RF) = 0.055 +/- 0.011), as well as the absolute absorption cross section of the D-5 <- D-0 excitation transition (sigma (abs) > 670 Mb). The former transition is responsible for the laser-induced and recurrent fluorescence of perylene, and the latter is the most prominent in the absorption spectrum. The vibrational cooling rate is found to be consistent with the simple harmonic cascade approximation. Quantitative experimental benchmarks of unimolecular processes in polycyclic aromatic hydrocarbon ions like perylene are important for refining astrochemical models.
|
|
