Drift velocity of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>in gases follows rarefied gas dynamics

Nanbu, Kenichi; Wakayama, Go

doi:10.1103/physreve.63.062201

Cited by 4 publications

(3 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As dictated by eq 2, the mobilities of tryptic peptide ions decrease slightly at high field strengths. As shown in Figure 5, a plot of K 0 vs. E 0 /p, this observation is also consistent with other IMS measurements on a wide range of analytes including atomic, small organic, and fullerene ions [37,38]. The representative data for the additional classes of ions shown in Figure 5 (Ar ϩ for the atomic ions, CH 3 CHOH ϩ for small organic ions, C 60 ϩ for fullerene ions, and NTDGSTDYGILQINSR for the [M ϩ H] ϩ tryptic peptide ions) were all acquired under conditions that minimize the influence of gas-phase chemistry on the mobility separation (i.e., low pressure, high gas purity, low relative humidity) and thus emphasizing the influence of ion transport at high field strengths on the separation, with the effect of high field diffusion more pronounced for the higher mobility species.…”

supporting

confidence: 77%

The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry

Ruotolo

McLean

Gillig

et al. 2005

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

The influence of field strength on the separation of tryptic peptides by drift tube-based ion mobility-mass spectrometry is reported. Operating the ion mobility drift tube at elevated field strengths (expressed in V cm Ϫ1 torr Ϫ1 ) reduces separation times and increases ion transmission efficiencies. Several accounts in the literature suggest that performing ion mobility separation at elevated field strength can change the selectivity of ion separation. To evaluate the field strength dependant selectivity of ion mobility separation, we examined a data set of 65 singly charged tryptic peptide ion signals (mass range 500 -2500 m/z) at six different field strengths and four different drift gas compositions (He, N 2 , Ar, and CH 4 ). Our results clearly illustrate that changing the field strength from low field (15 V cm Ϫ1 torr Ϫ1) to high field (66 V cm Ϫ1 torr Ϫ1 ) does not significantly alter the selectivity or peak capacity of IM-MS. The implications of these results are discussed in the context of separation methodologies that rely on the field strength dependence of ion mobility for separation selectivity, e.g., high-field asymmetric ion mobility spectrometry ( H ybrid mass spectrometry techniques have emerged as powerful tools for complex mixture analysis. For example, several groups have used liquid chromatography-mass spectrometry (LC-MS) for identification of components of simple proteomes, and have reported enhanced sequence coverage, limit-of-detection, dynamic range, and peak capacity relative to MS-only methods of analysis [1,2]. Prior to the development of LC-MS techniques for proteomics, mass spectrometry of 2-D gel-separated proteins was the method of choice for large-scale protein identification, because the method provides both excellent peak capacity and modestly improved dynamic range [3,4]. However, both LC and 2-D gel separations inefficiently utilize MS detection, because separations can take 5 to 10 orders of magnitude longer than necessary for mass spectrometry detection (i.e., Ͻ100 s for time-of-flight (TOF) MS) [5].Ion mobility (IM) separation (based on ion collision cross-section) coupled with mass spectrometry possesses many of the same advantages of LC-MS approaches, i.e., enhanced dynamic range and increased peak capacity when compared with MS-only analysis [6,7]. Further, IM separations require only milliseconds (typically 500 s to 2 ms for tryptic peptides), which is better suited to MS timescales [8]. For example, both Russell (using matrix assisted laser desorption ionization -MALDI) and Clemmer (using electrospray ionization -ESI) have utilized IM-MS for the analysis of complex protein mixtures [9,10]. In the case of MALDI-IM-MS protein mixture analysis, the hybrid separation technique provided enhanced percent amino acid sequence coverage through the increased dynamic range relative to MS-only analysis [9]. Clemmer and coworkers used LC-ESI-IM-MS to analyze biologically derived complex mixtures, and demonstrated that the combination of LC and IM provides complementary separation...

show abstract

supporting

confidence: 77%

The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry

Ruotolo

McLean

Gillig

et al. 2005

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…In addition, recent results from our laboratory also suggest that the K o values for peptide ions in the range of 500 -2500 are relatively unaffected by increased field strength up to 66 V cm Ϫ1 torr Ϫ1 (ϳ200 Td) [25]. In most cases where the field-strength dependant mobility of large ions has been investigated, a slight mass dependant decrease in the apparent ion mobility is typically observed at high field strengths [26]. According to the theoretical constructs presented here, a decrease in ion mobility will only aid the acquisition of low-field, diffusion-limited resolution.…”

Section: Discussionmentioning

confidence: 89%

Resolution equations for high-field ion mobility

Verbeck

Ruotolo

Gillig

et al. 2004

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

An extension of current mobility resolution equations as they apply to high-field ion mobility spectrometry is presented. The new resolution expression is applied to arrival time distributions for ions having a large range of ion mobilities and mass-to-charge ratios (m/z). The results indicate that the new equation can be utilized to predict the mobility resolution over a broader range of applied electric fields than previous ion mobility resolution expressions. (J Am Soc Mass Spectrom 2004, 15, 1320 -1324) © 2004 American Society for Mass Spectrometry S eparation based on the mobility of an ion through a neutral buffer gas (i.e., ion mobility spectrometry (IMS)) [1,2] is an important technology for studying long-lived electronic states of gas-phase ions and a sensitive method for detection of air-borne species [3, 4]. Recent work, which demonstrates the utility of IMS for analyzing gas-phase ionized biopolymers (i.e., peptides, proteins, DNA, etc.), has renewed interest in the analytical applications of IMS and led to the development of several high-resolution drift tubes in combination with mass spectrometry [5][6][7][8][9][10][11]. In order to perform a gas-phase separation of near thermal, structurally isomeric gas-phase ion populations, most IMS separations are performed near the low-field limit. Low-field conditions are important for studies of gas-phase peptide/protein structure because collisional activation can, in some cases, lead to structural rearrangement and/or fragmentation.In addition to the distinctions drawn for IMS operation in terms of separation field strength, the use of IMS can be divided into two pressure regimes, viz. high pressure (typically low-field) and low pressure (either low or high applied fields), and there are distinct advantages associated with both pressure regimes. At high pressure, the number of ion-neutral collisions is high, i.e., C 60 ϩ⅐ undergoes 10 10 collisions/s at 760 torr He compared with about 10 7 collisions/s for the same ion at 1 torr He. It is also important to consider that collisions with low-level impurities may significantly influence the separation and total drift time of an analyte ion. For example, in a 30 cm drift cell maintained at 760 torr He, C 60 ϩ⅐ will undergo 10 5 -10 6 collisions with a of 0.01% impurity, compared with ca. 10 collisions with the same level of impurity at 1 torr He. Another advantage of low-pressure drift tubes is the ease of coupling ion mobility with high vacuum mass spectrometers. Lastly, low-pressure (or high-field) mobility decreases ion separation times, leading to higher throughput analysis (approximately 3 orders of magnitude faster for analysis times at 1 torr over 760 torr).Low-field mobility conditions are defined in terms of the kinetic energy acquired by the ion in the presence of an applied field (E o ). That is, the translational energy gained by the ion between collisions should be less than the thermal energy of the collision gas [12, 13],where m is the mass of the ion, M is the mass of the neutral drift gas, ...

show abstract

“…The potential that is time-modulated by high frequency biasing is well approximated by the exponentially attenuating sine curve. In this case, the velocity of ion normal to the wafer, v w , can be expressed as v w = v w +v w , where v w is the contribution from a time-averaged potential and v w is that from an oscillatory part of the potential [10]. For high frequency biasing, we found that the time when the ion impinges on the wafer is uniformly distributed.…”

Section: Analytical Ion Velocity Distributionmentioning

confidence: 88%

Velocity distribution of ions incident on a radio-frequency biased wafer

Wakayama¹,

Nanbu²

2001

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. The ion velocity distribution (IVD) is important in plasma etching of microfeatures. IVD at a rf biased wafer is studied, first analytically using probability theory and then numerically by using a particle simulation method. The analytic expression shows that IVD is governed by the parameter qVri/miuil, where q is the charge of ion, V T f is the rf bias amplitude, w is the rf bias angular frequency, I is the penetration depth of bias potential, and mi is the mass of ion. The analytical expression is applicable to the case when the ion collisions in the penetration depth are negligibly few and the rf period of biasing is much shorter than the time that ions take in traversing the depth I. The IVDs for general conditions are also examined using the self-consistent particle-in-cell/Monte Carlo simulation. I INTRODUCTIONWeakly ionized plasmas used in materials processing generally consist of positive and negative ions, electrons, and neutral species. In the case when electrons are more abundant than negative ions, a negative potential is formed near the surface of the floating wafer immersed in the plasma. In processing plasmas the electron temperature is few electron volts, while the ion temperature is roughly equal to the background gas temperature. To keep the balance between the negative and positive currents on the floating surface, low energy electrons should be reflected in the sheath region back to the plasma bulk. This is the physical reason why the potential of the floating wafer is lower than the plasma potential.Negative sheath potential (measured from the plasma bulk) accelerates the positive ions to the wafer. If no collision is assumed in the sheath region, the positive ions impinge almost perpendicularly onto the wafer. However, electrons are decelerated and lose the velocity component normal to the wafer.When ions and electrons come into a microscopic trench, electrons are easily sticked near the top of the side of the trench wall while ions can reach the bottom of the trench. This kind of charge separation inside microfeatures causes a charge build-up. The strongly localized electric field due to the charge build-up distorts the trajectories of incident ions, which results in an anomalous etch profile called "notching". The localized charge build-up also causes the electrical breakdown induced by fatal tunneling currents through gate-oxides.In order to suppress the so-called charging damages, new ideas on plasma sources are proposed, e.g., timemodulation of the source power [1] and use of ultra-high frequency (500 MHz) power [2]. These approaches are intended to lower the electron temperature and hence generate more negative ions. To understand the role of negative ions, let us consider the plasma including only positive and negative ions; when the wafer is biased at low frequency (< 3MHz), the positive and negative ions impinge on the bottom of the trench alternately. Thus no charge build-up occurs.The ion energy distribution (IED) and ion angle distribution (IAD) of ions that impinge o...

show abstract

Drift velocity ofC60+in gases follows rarefied gas dynamics

Abstract: The drift velocities of C(60)(+) in He, Ne, Ar, and Kr were found to be estimated with high accuracy using the drag coefficient of a solid body in free molecule flow. That is, massive C(60)(+) behaves in gases as if it were a large classical body.

Cited by 4 publications

References 4 publications

The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry

The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry

Resolution equations for high-field ion mobility

Velocity distribution of ions incident on a radio-frequency biased wafer

Contact Info

Product

Resources

About