Efficient radiative cooling of tetracene cations C18H12+: absolute recurrent fluorescence rates as a function of internal energy. Issue 15 (31st March 2023)

• Record Type: Journal Article
• Authors: Bernard, Jérôme; Ji, MingChao; Indrajith, Suvasthika; Stockett, Mark H.; Navarro Navarrete, José E.; Kono, Naoko; Cederquist, Henrik; Martin, Serge; Schmidt, Henning T.; Zettergren, Henning
• Is Part Of: Physical chemistry chemical physics. Volume 25:Issue 15(2023)
• Page Start: 10726
• Page End: 10740
• Publication Date: 2023-03-31
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d3cp00424d
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : High recurrent fluorescence rates of tetracene cations, C18 H12, measured with two electrostatic ion rings, DESIREE and Mini-Ring, lead to much more effective radiative cooling than previously investigated PAH cations. Abstract : We have measured recurrent fluorescence (RF) cooling rates of internally hot tetracene cations, C18 H12 +, 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.