Jet-cooled molecules

M. Herman, R. Georges, M. Hepp, and D. Hurtmans, High resolution Fourier transform spectroscopy of jet cooled molecules. Int. Rev. Phys. Chem. 19, 277 325 (2000). 

Wilhelm, U. Aicher, K.P. Grotemeyer, J. Ion Storage Combined With Reflec-tron TOF Mass Spectrometry Ion Cloud Motions As a Result of Jet-Cooled Molecules. Int. J. Mass Spectrom. Ion Proc. 1996,152, 111-120. 

Figure 2.7 Vibrational excitation spectra in the region of the fundamental N-H and C-H symmetric stretches of pyrrole (a) photoacoustic Raman spectrum in a static cell at a pressure of 6.5 Torr and (b) H action spectrum obtained by 243.135 nm dissociation of jet-cooled molecules at a delay of 10 ns between the SRS and UV beams. The intensity scale of each panel is different. Reproduced with permission from Ref. [87]. Copyright (2011) AlP Publishing LLC.

Figure 8.4. Inversion of 9,10-dihydroanthracene in the excited singlet state, (a) The equilibrium bent shape of excited molecule, (b) the double-well potential for inversion, and (c) the fluorescence excitation spectrum of the jet-cooled molecule. (From Chakraborthy and Choudhury [1990].)...

V. Vaida, Acc. Chem. Res., 19, 114 (1986). Electronic Absorption-Spectroscopy of Jet-Cooled Molecules. 

Fig. 6 and 7 display typical results for the effect of solvent on the excitation spectra, fluorescence and lifetimes. We used these observations to measure bond dissociation energy of the different species by varying the excess vibrational energy of the parent jet-cooled molecule type modes. The threshold effect found for the dissociation of the 1 1 IQ (methanol) is evident and occurs at ca. 3 kcal mol , in agreement with solution-phase enthalpies. (The effect of higher degree of solvation on the dynamics will be discussed elsewhere.)... 

Vaida V (1986) Electronic spectroscopy of jet-cooled molecules. Acc Chem Res 19 114-120... 

Schroeder J 1997 Picosecond kinetics of trans-cis photoisomerisations from jet-cooled molecules to compressed solutions Ber. Bunsenges Phys. Chem. 101 643... 

Conformational changes in molecules often proceed along vibrational pathways. In selected cases these pathways can be represented by one- or two-dimensional vibrational potential energy sur ces (PESs). In oiu laboratory we have for many years investigated the PESs of cyclic andbicyclic molecules in their electronic ground states using far-in rared and Raman spectroscopy.In recent years we have also used fluorescence spectra of jet-cooled molecules and ultraviolet absorption spectra to determine the PESs in electronic excited states. In the present paper we present our results for the ground (So) and excited [Si(7t,7t ")] electronic states of several molecules in the indan family which are shown in Scheme I. 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

K. Le Barbu, V. Brenner, Ph. Millie, F. Lahmani, and A. Zehnacker Rentien, An experimental and theoretical study of jet cooled complexes of chiral molecules The role of dispersive forces in chiral discrimination. J. Phys. Chem. A 102, 128 137 (1998). 

The yttrium monocarbide molecule was only recently observed under high resolution by Simard et al. (37) using Jet-cooled optical spectroscopy. The ground electronic state was determined to be an 0=5/2 state, which was consistent with the ab initio calculations of Shim et al. (38) who predicted a 11 ground state for YC in CASSCF calculations. The experimental work of Simard et al. yielded estimates for both the bond length and harmonic frequency of YC. In addition to their CASSCF calculations. Shim et al. (38) also reported results from mass spectrometric equilibrium experiments, which resulted in a bond dissociation energy of Do = 99.0 3.3 kcal/mol. The results from the present work are shown in Table I. An open-shell coupled cluster singles and doubles... 

K. Kleinermanns, M. Gerhards and M. Schmitt, Electronic spectroscopy of aromatic molecules in jet-cooled hydrogen bonded clusters - structure and fluxionality, Her. Bunsen-Ges. Phys. Chem., 101 (1997) 1785-1798. 

The jet-cooled species can be studied using standard laser techniques (Figure 13-4a) like laser-induced fluorescence (LIF or fluorescence excitation spectroscopy) or R2PI, as well as using their sophisticated double-resonance variants, like UV/UV or IR/UV double resonance spectroscopy (Figure 13-4b and 4c), to investigate molecules or clusters existing under various isomeric forms... 

Fig. 4. An ortho-methyl group in diethylamino-pyrimidin induces some ground state twist and hence energetically destabilizes the B state but not yet sufficiently to make the population of the A state a najor process in supersonic jet spectroscopy. Upper panel dispersed fluorescence spectra of the jet-cooled bare molecule [36]. In clusters with methanol, the TICT state is preferentially lowered, and the majority of the ob rved red-shifted fluorescence can be assign l to arise from the TICT state (lower panel). This does not occur for the compound without an ortho-methyl group.

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