Velocity Modulation Spectroscopy of Ions

Stephenson, Serena K.; Saykally, Richard J.

doi:10.1021/cr040100d

Cited by 54 publications

(38 citation statements)

References 159 publications

(302 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Comb-vms combines cavity-enhanced direct frequency comb spectroscopy [37,38,39] with velocity-modulation spectroscopy [40,41,42,43] for discrimination between ions and neutral species. This technique could also be readily extended to the detection of radicals by concentration modulation.…”

Section: Comb-vmsmentioning

confidence: 99%

Broadband velocity modulation spectroscopy of HfF+: Towards a measurement of the electron electric dipole moment

Cossel

Gresh

Sinclair

et al. 2012

Chemical Physics Letters

View full text Add to dashboard Cite

Precision spectroscopy of trapped HfF + will be used in a search for the permanent electric dipole moment of the electron (eEDM). While this dipole moment has yet to be observed, various extensions to the standard model of particle physics (such as supersymmetry) predict values that are close to the current limit. We present extensive survey spectroscopy of 19 bands covering nearly 5000 cm −1 using both frequency-comb and single-frequency laser velocity-modulation spectroscopy. We obtain high-precision rovibrational constants for eight electronic states including those that will be necessary for state preparation and readout in an actual eEDM experiment.

show abstract

Section: Comb-vmsmentioning

confidence: 99%

Broadband velocity modulation spectroscopy of HfF+: Towards a measurement of the electron electric dipole moment

Cossel

Gresh

Sinclair

et al. 2012

Chemical Physics Letters

View full text Add to dashboard Cite

show abstract

“…In velocity modulation spectroscopy [46], an alternating electric field is applied in the longitudinal direction in the plasma. The resulting oscillating velocity of the ions along the laser path gives an oscillating Doppler shift, which can be demodulated to give a highly effective way of extracting the ion light-absorption signal from the massive background signal of (unmodulated) neutral species, which also absorb light.…”

Section: Direct Absorption Spectroscopy In Plasmasmentioning

confidence: 99%

Ion spectroscopy: Where did it come from; where is it now; and where is it going?

Baer¹,

Dunbar

2010

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

a large group of mass spectrometrists working in the area of ion spectroscopy. In this introduction to the field, we provide a brief history, its current state, and where it is going. Ion spectroscopy of intermediate size molecules began with photoelectron spectroscopy in the 1960s, while electronic spectroscopy of ions using the photodissociation "action spectroscopic" mode became active in the next decade. These approaches remained for many years the main source of information about ionization energies, electronic states, and electronic transitions of ions. In recent years, highresolution laser techniques coupled with pulsed field ionization and sample cooling in molecular beams have provided high precision ionization energies and vibrational frequencies of small to intermediate sized molecules, including a number of radicals. More recently, optical parametric oscillator (OPO) IR lasers and free electron lasers have been developed and employed to record the IR spectra of molecular ions in either molecular beams or ion traps. These results, in combination with theoretical ab initio molecular orbital (MO) methods, are providing unprecedented structural and energetic information about gas-phase ions. (J Am Soc Mass Spectrom 2010, 21, 681-693) © 2010 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry T here are at least three perspectives guiding research in molecular spectroscopy of ions, which have given rise to rather distinct research communities. First is the goal of finding the quantum energy levels (electronic, vibrational, rotational) with high accuracy and energy resolution. Benefiting from experimental convenience, a vast body of results of this sort has been accumulated from photoionization and photoelectron spectroscopy experiments where the initial sample is the neutral molecule corresponding to an ion of interest.Second is the question of "what color" the ion is, that is to say, taking the ion itself as the sample, observing the wavelengths and transition intensities of the optical absorptions or emissions of the ion. These experiments are difficult, but have great interest for the study of ions found in nature, as for instance among the community of astronomers trying to sort out the telescope spectra corresponding to molecular species existing in extraterrestrial environments.Third is the use of spectra as a window to the identification and structural characterization of ionic molecules formed from interesting precursors by any of a variety of ionization, ion-molecule reaction, or ionextraction techniques. Combined with mass spectrometry, this branch of ion spectroscopy has developed into a new structural approach comparable to MS/MS, thanks to its ability to distinguish small conformational or structural differences among iso-mass ions. These studies have been dominated by the use of "action spectroscopy" (multi-photon and ion tagging dissociation techniques) to provide convenient, although indirect, access to the spectra of interesting ions.The three major parts of thi...

show abstract

“…4 The invention of velocity modulation spectroscopy (VMS), 5 which involves using a high voltage AC discharge to modulate the velocity of ions and a lock-in amplifier to isolate the modulated ionic absorption signals from the unmodulated neutral signals, has allowed for the spectroscopic study of scores of molecular ions. 4 However, due to harsh plasma conditions, molecular ions produced in VMS experiments often have high rotational and vibrational temperatures, typically on the order of several hundred Kelvin. For example, CH + 3 has been studied by Oka and coworkers in a liquid nitrogen cooled discharge cell, where the rotational and vibrational temperatures were reported as 371 and 700 K, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…11 The only published highresolution spectrum of CH + 5 was recorded by Oka and coworkers 12 in a liquid nitrogen cooled discharge of H 2 and CH 4 , and was identified by a process of elimination, by removing the known spectral lines of H + 3 , CH + 3 , C 2 H + 3 , HCO + , HCNH + , the Rydberg spectrum of H 2 , and strong lines of CH 4 that remained due to a slight asymmetry in the AC plasma. This rich spectrum (∼900 lines, due to the fairly high rotational temperature) may still contain some transitions of other ions, and almost certainly is missing some CH + 5 transitions due to overlap with CH 4 lines.…”

Section: Introductionmentioning

confidence: 99%

“…14 Their spectrum evidently contains not only many transitions that coincide with those of Oka and co-workers, but also many transitions that do not. Because of the lack of a rigorous ion/neutral discrimination, it is possible that some of these transitions may be due to excited CH 4 . They have proposed 13 the use of four-line combination differences to help assign the spectrum, but this effort requires higher precision in the determination of line centers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam

Mills

Siller

Porambo

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

Direct spectroscopy of a fast molecular ion beam offers many advantages over competing techniques, including the generality of the approach to any molecular ion, the complete elimination of spectral confusion due to neutral molecules, and the mass identification of individual spectral lines. The major challenge is the intrinsic weakness of absorption or dispersion signals resulting from the relatively low number density of ions in the beam. Direct spectroscopy of an ion beam was pioneered by Saykally and co-workers in the late 1980s, but has not been attempted since that time. Here, we present the design and construction of an ion beam spectrometer with several improvements over the Saykally design. The ion beam and its characterization have been improved by adopting recent advances in electrostatic optics, along with a time-of-flight mass spectrometer that can be used simultaneously with optical spectroscopy. As a proof of concept, a noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup with a noise equivalent absorption of ∼2 × 10 −11 cm −1 Hz −1/2 has been used to observe several transitions of the Meinel 1-0 band of N + 2 with linewidths of ∼120 MHz. An optical frequency comb has been used for absolute frequency calibration of transition frequencies to within ∼8 MHz. This work represents the first direct spectroscopy of an electronic transition in an ion beam, and also represents a major step toward the development of routine infrared spectroscopy of rotationally cooled molecular ions.

show abstract

Velocity Modulation Spectroscopy of Ions

Cited by 54 publications

References 159 publications

Broadband velocity modulation spectroscopy of HfF+: Towards a measurement of the electron electric dipole moment

Broadband velocity modulation spectroscopy of HfF+: Towards a measurement of the electron electric dipole moment

Ion spectroscopy: Where did it come from; where is it now; and where is it going?

Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam

Contact Info

Product

Resources

About