New Method for Double-Resonance Spectroscopy in a Cold Quadrupole Ion Trap and Its Application to UV–UV Hole-Burning Spectroscopy of Protonated Adenine Dimer

Abstract

A novel method for double-resonance spectroscopy in a cold quadrupole ion trap is presented, which utilizes dipolar resonant excitation of fragment ions in the quadrupole ion trap. Photofragments by a burn laser are removed by applying an auxiliary RF to the trap, and a probe laser detects the depletion of photofragments by the burn laser. By scanning the wavelength of the burn laser, conformation-specific UV spectrum of a cold ion is obtained. This simple and powerful method is applicable to any type of double-resonance spectroscopy in a cold quadrupole ion trap and was applied to UV-UV hole-burning spectroscopy of protonated adenine dimer. It was found that protonated adenine dimer has multiple conformers/tautomers, each with multiple excited states with drastically different excited state dynamics.

Photodissociation Electronic Spectra of Cold Protonated Quinoline and Isoquinoline in the Gas Phase

“…Supplementary do not differ much in energy from those of its structural isomer. In-plane iQH + vibrational modes [28][29][30][31][32][33] are again active in S 1 , the same three modes, exp = 588 cm 1 ( 30 , symmetrical ring deformation), exp = 486 cm 1 ( 31 , symmetrical breathing) and exp = 467 cm 1 ( 32 , 14 nonsymmetrical breathing) prevailing. The modes [30][31][32] …”

“…Left, protonated quinoline (quinolinium ion, QH + ); right, protonated isoquinoline (isoquinolinium ion, iQH + ). Additionally, a double resonance method 29 can be applied to a determined ion in the trap in order to discriminate whether the observed spectral bands belong to a unique species (different transitions sharing the same ground state) or originate from different conformers (further details in the Supporting Information file).…”

Communication: UV photoionization of cytosine catalyzed by Ag+

“…34 The CytAg + complex is re-isolated by removing the remaining Cyt 2 Ag + and other fragment ions from the QIT by resonantly exciting its axial micromotion with an auxiliary dipolar Radio Frequency (RF) as reported in a previous work. 38 A second photo-dissociation tunable laser (laser 2) excites the isolated CytAg + complex, around 60 ms after laser 1. The fragment and parent CytAg + ions are then extracted to the TOF mass spectrometer.…”

Vibronic spectra of protonated hydroxypyridines: contributions of prefulvenic and planar structures

“…We have used the tickle method initially proposed by Kang et al, 38 which consists of applying on one cap of the QIT an auxiliary RF whose frequency is tuned to selectively eject a given ionic fragment. By doing that, the chosen ionic fragment of a first UV laser (burn), set on a given vibronic band, is ejected from the trap, which allows recording the signal induced by a second UV laser (probe) scan, over the whole spectral range, without background signal.…”