Matrix isolation of acetonitrile clusters from a pulsed supersonic beam

Knözinger, Erich; Beichert, P.; Hermeling, J.; Schrems, Otto

doi:10.1021/j100109a013

Cited by 19 publications

(16 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The appearance of larger acetonitrile clusters should become more likely for significantly higher deposition rates. So far such large spe- cies have, however, only been observed after adiabatic instead of thermal effusive expansion prior to deposition [5].…”

Section: Resultsmentioning

confidence: 97%

“…In fact, this barrier is likely to be smaller for HTM because its unit cell structure (Fig. 2b) is based on pairs of antiparallel oriented acetonitrile molecules as elementary constituents [3,5]. In order to build up the LTM from antiparallel dimers a considerable amount of energy has to be invested for the reorientation of acetonitrile monomers out of the energetically favoured geometry in the stable dimer (Figs.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Gas-phase deposition of acetonitrile: an attempt to understand Ostwald’s step rule on a molecular basis

Tizek

Grothe

Knözinger

2004

Chemical Physics Letters

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Gas-phase deposition of acetonitrile: an attempt to understand Ostwald’s step rule on a molecular basis

Tizek

Grothe

Knözinger

2004

Chemical Physics Letters

View full text Add to dashboard Cite

“…This is comparable to the methanol dimer bond energy, which is reported within a range of 3.45 eV [45] to 6.04 eV [37], suggesting that the density of acetonitrile dimer may be comparable to that for methanol dimer. Significant dimer:monomer ratios have been measured in supersonic expansions [46]; however, this is not representative of the high-temperature environment of an APPI source.…”

Section: Generation Of Solvent Ions From Acetonitrile With Appimentioning

confidence: 97%

APPI-MS: Effects of mobile phases and VUV lamps on the detection of PAH compounds

Short¹,

Cai²,

Syage³

2007

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

The technique of atmospheric pressure photoionization (APPI) has several advantages over electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), including efficient ionization of nonpolar or low charge affinity compounds, reduced susceptibility to ion suppression, high sensitivity, and large linear dynamic range. These benefits are greatest at low flow rates (i.e., Յ100 L/min), while at a higher flow, photon absorption and ion-molecule reactions become significant. Under certain circumstances, APPI signal and S/N have been observed to excel at higher flow, which may be due to a nonphotoionzation mechanism. To better understand APPI at higher flow rates, we have selected three lamps (Xe, Kr, and Ar) and four mobile phases typical for reverse-phase, high-pressure liquid chromatography: acetonitrile, methanol, (1:1) acetonitrile:water and (1:1) methanol:water. As test compounds, three polyaromatic hydrocarbons are studied: benzo[a]pyrene, indeno [1,2,3-c, d]pyrene and benz [a]anthracene. We find that solvent photoabsorption cross-section is not the only parameter in explaining relative signal intensity, but that solvent photo-ion chemistry can also play a significant role. Three conclusions from this investigation are: (1) [4,5]. Recent work has focused on the direct comparison of different sources (APPI, APCI, and ESI) with specific target compounds, e.g., polyaromatic hydrocarbons [6,7], hydrophobic peptides [8], pesticides [9,10], as well as fatty acids and lipids [4,5]. In many cases atmospheric pressure photoionization (APPI) [1,7] has demonstrated extended linear dynamic range [11], enhanced sensitivity and thus lower detection limits [6,9,[12][13][14][15], and reduced or no off-line sample cleanups [6,9] in comparison with direct APCI or ESI. Adding a dopant (dopant-assisted, DA) to the mobile phase in many cases can further increase sensitivity [2].A related analytical technique is atmospheric pressure laser ionization (APLI), which has shown excellent sensitivity for certain non-or low-polar compounds [3]. The enhanced sensitivity is a direct result of the high photon flux associated with a laser system, often several orders of magnitude higher than the noncoherent light sources, e.g., lamps used with APPI. The APLI source relies on one-color, two-photon (1 ϩ 1) resonantlyenhanced multiphoton ionization (REMPI), typically using a KrF excimer laser emitting light at 5.0 eV, efficiently ionizing nonpolar molecules. However, APLIis not yet widely used due to the large size, expense, and maintenance associated with the laser system. Furthermore, changing the wavelength of an excimer laser requires the replacement of the gas mixture and often re-tuning of the laser cavity, whereas with an APPI system, the wavelength can be changed by simply switching the lamp.To improve the capabilities of APPI for LC-MS, we have focused on the ion chemistry involved in and following the photoionization process. Although direct, single-photon ionization (SPI) of a compound [M] however, there is litt...

show abstract

“…42 Acetonitrile clusters have already been the subject of both experimental and theoretical studies. [43][44][45][46][47][48][49][50][51][52][53] Because of the large dipole moment of acetonitrile ͑3.9 D͒, the interactions within these clusters are dominated essentially by dipole-dipole forces, and the lowest energy structures reflect the favorable antiparallel pairing of the molecular dipoles. Molecular dynamics ͑MD͒ and Monte Carlo ͑MC͒ studies have shown that the antiparallel pairing of the dipoles may lead to rigid solidlike structures of the n-even clusters with melting transition temperatures considerably higher than those of the n-odd clusters.…”

Section: Introductionmentioning

confidence: 99%