Energy redistribution in large molecules. Direct study of intramolecular relaxation in the gas phase with picosecond gating

1983 ◽  
Vol 75 ◽  
pp. 331 ◽  
Author(s):  
Robert Moore ◽  
Fuad E. Doany ◽  
Edwin J. Heilweil ◽  
Robin M. Hochstrasser
Keyword(s):  
Gas Phase ◽  
Energy Redistribution ◽  
Large Molecules ◽  
Direct Study

scholarly journals Laboratory formation of large molecules in the gas phase

2019 ◽  
Vol 623 ◽  
pp. A102 ◽  
Author(s):  
Junfeng Zhen
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Quadrupole Ion Trap ◽  
Molecular Clusters ◽  
Large Molecules ◽  
Flight Mass Spectrometry ◽  
Molecular Precursor ◽  
Dust Grain ◽  
Strong Radiation ◽  
Graphene Cluster

We report the experimental study on the formation process of large molecules (e.g. a family group of molecular clusters and graphene) in the gas phase. The experiment was carried out using a quadrupole ion trap in combination with time-of-flight mass spectrometry. As the initial molecular precursor, dicoronylene (DC, C48H20)/anthracene (C14H10) cluster cations, the results show that large PAH cluster cations (e.g., (C14H10)C48Hn+, n = [1–19] and (C14H10)C62Hm+, m = [1–25]) and PAH-graphene cluster cations (e.g., (C14H10)nC48+, n = 0, 1, 2, 3 and (C14H10)mC62+, m = 0, 1, 2) are formed by gas-phase condensation under laser irradiation conditions. We infer that these results present in here provide a formation route for interstellar large molecules under the influence of a strong radiation field in the ISM. The relevance of newly formed species to the nanometer-sized dust grain in space is briefly discussed.

Effective method to compute vibrationally resolved optical spectra of large molecules at finite temperature in the gas phase and in solution

2007 ◽  
Vol 126 (18) ◽  
pp. 184102 ◽  
Author(s):  
Fabrizio Santoro ◽  
Alessandro Lami ◽  
Roberto Improta ◽  
Vincenzo Barone
Keyword(s):  
Gas Phase ◽  
Finite Temperature ◽  
Optical Spectra ◽  
Large Molecules

STUDIES OF ELECTRONIC PROPERTIES OF MEDIUM AND LARGE MOLECULES ORIENTED IN A STRONG UNIFORM ELECTRIC FIELD

2001 ◽  
Vol 15 (27) ◽  
pp. 3471-3502 ◽  
Author(s):  
WEI KONG
Keyword(s):  
Electric Field ◽  
Small Molecules ◽  
Gas Phase ◽  
Variation Method ◽  
Detailed Knowledge ◽  
Translational Energy ◽  
Spectroscopic Techniques ◽  
Transition Dipole ◽  
Polarization Spectroscopy ◽  
Large Molecules

Polarization spectroscopy of oriented gas phase medium and large molecules achieved via a uniform DC electric field provides a means to determine the direction of transition dipoles. In this article, the theoretical background of this orientation method, its characterization, and its application in studies of electronic transitions, will be presented. Mature gas phase spectroscopic methods have been developed for studies of small molecules, but studies of medium to large sized species are faced with special challenges. These challenges arise from differences between large and small molecules: large systems typically exhibit fast internal conversion, slow dissociation, and low translational energy release upon dissociation. Thus conventional gas phase spectroscopic techniques are not applicable to derive the direction of the transition dipole. DC induced orientation offers a solution to this problem. It is ideal for studies of systems with small rotational constants and large permanent dipoles, even when a detailed knowledge of the molecular structure, such as the direction of the permanent dipole in the molecular frame, is unknown. The degree of orientation can be calculated using the linear variation method, given the rotational temperature and the size of the permanent dipole. The associated experimental observables can be used to confirm the effect of orientation, or to determine the direction of a transition dipole. These observables include the ratio of excitation probabilities under different polarization directions and spectroscopic features. In some cases, the direction and size of the permanent dipole of the excited electronic state can also be determined. Examples of this type of polarization spectroscopy are presented for asymmetric tops such as diazines, acetelye-HF clusters, nitroaromatics and butyl nitrite. Illustrations of pendular states and its application in linear and diatomic molecules are also briefed. Applications of this method for studies of large molecules and potential pitfalls will be discussed.

scholarly journals Picosecond Laser Chemistry in Supersonic Jet Beams

1983 ◽  
Vol 2 (3-4) ◽  
pp. 55-76 ◽  
Author(s):  
Ahmed H. Zewail
Keyword(s):  
Supersonic Jet ◽  
Picosecond Laser ◽  
Threshold Effect ◽  
Quantum Beats ◽  
Energy Redistribution ◽  
Laser Chemistry ◽  
Large Molecules ◽  
Rrkm Calculation ◽  
Statistical Behavior

In this review we describe the development and the applications of the picosecond-jet technique, which utilizes a picosecond laser and a supersonically-cold jet beam of large molecules. The applications include studies of coherence (quantum beats), photodissociation, isomerization, and partial solvation. The results emphasize the role of intramolecular energy redistribution, and provide evidence for intramolecular threshold effect for rates vs. excess molecular energy. Simple theory for this redistribution of energy among certain modes in molecules is given, and comparison with RRKM calculation is also made to assess the nature of the statistical behavior for the redistribution.

A fluorescence detection scheme for ultra large molecules after gas phase separation

Talanta ◽  
2007 ◽  
Vol 71 (5) ◽  
pp. 2126-2128 ◽  
Author(s):  
J HE ◽  
W ZHONG ◽  
A TANG ◽  
X YAN ◽  
C LEWIS ◽  
...  
Keyword(s):  
Phase Separation ◽  
Gas Phase ◽  
Fluorescence Detection ◽  
Detection Scheme ◽  
Large Molecules ◽  
Gas Phase Separation
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