Sm Vapor Research Articles

Selective recovery of Sm from Sm-Co magnet scrap by vacuum distillation

Sm-Co rare earth permanent magnet materials are widely used in special fields such as new energy and electronic information. Sm-Co permanent magnet scraps are generated during the preparation and the use of end-of-life permanent magnets, which need to be recycled for the sustainable development. It is proposed to selectively recover Sm from the Sm-Co permanent magnet scraps by vacuum distillation. The experimental investigations were carried out in a vacuum furnace with double temperature zones for the efficient condensation of Sm vapor based on the thermodynamic and kinetic calculations. The recycling feasibility of the recovery of rare earth and the evaporation mechanism of Sm were also demonstrated in this work. The results show that Sm with the purity over 99% was obtained by the molybdenum condenser used as a condensing collectors at given conditions, providing a reference for the pyrometallurgical recovery of rare earth secondary resources.

Electronic Spectroscopy of SmO in the 645 to 670 nm Range.

The associative ionization reaction Sm + O → SmO+ + e- is being investigated as an electron source that could transiently modify high-altitude electron densities via Sm vapor release. Electronic spectra have been obtained from tests where sounding rockets released Sm vapor, but the interpretation of these results has been hampered by the limited laboratory spectral data available for both SmO and SmO+. The present study extends the spectroscopic characterization of SmO in the 645-670 nm range, where the field data show the most prominent molecular emission features. Rotationally resolved excitation spectra, dispersed laser-induced fluorescence spectra, and fluorescence decay lifetimes are reported. The results are consistent with the assignment of a subset of the red-region bands to configurational transitions of the form Sm2+(4f56s)O2- ↔ Sm2+(4f55d)O2-. Analysis of the excited state hyperfine structure supports this configurational description.

Sulfur mustard corneal injury is associated with alterations in the epithelial basement membrane and stromal extracellular matrix

Sulfur mustard (SM; bis(2-chloroethyl) sulfide) is a highly reactive bifunctional alkylating agent synthesized for chemical warfare. The eyes are particularly sensitive to SM where it causes irritation, pain, photophobia, and blepharitis, depending on the dose and duration of exposure. In these studies, we examined the effects of SM vapor on the corneas of New Zealand white male rabbits. Edema and hazing of the cornea, signs of acute injury, were observed within one day of exposure to SM, followed by neovascularization, a sign of chronic or late phase pathology, which persisted for at least 28 days. Significant epithelial-stromal separation ranging from ~8–17% of the epithelial surface was observed. In the stroma, there was a marked increase in CD45+ leukocytes and a decrease of keratocytes, along with areas of disorganization of collagen fibers. SM also disrupted the corneal basement membrane and altered the expression of perlecan, a heparan sulfate proteoglycan, and cellular fibronectin, an extracellular matrix glycoprotein. This was associated with an increase in basement membrane matrix metalloproteinases including ADAM17, which is important in remodeling of the basement membrane during wound healing. Tenascin-C, an extracellular matrix glycoprotein, was also upregulated in the stroma 14–28 d post SM, a finding consistent with its role in organizing structural components of the stroma necessary for corneal transparency. These data demonstrate that SM vapor causes persistent alterations in structural components of the cornea. Further characterization of SM-induced injury in rabbit cornea will be useful for the identification of targets for the development of ocular countermeasures.

A Novel Topical Ophthalmic Formulation to Mitigate Acute Mustard Gas Keratopathy In Vivo: A Pilot Study.

PurposeThis pilot study investigated the in vivo therapeutic potential and tolerability of a multimodal ophthalmic formulation, topical eye drops (TED), for acute mustard gas keratopathy (MGK) using a rabbit model.MethodsTwenty New Zealand White rabbits were used. Only right eyes of 18 rabbits (oculus dexter [OD]) received single sulfur mustard gas (SM) vapor injury, whereas contralateral eyes were left untreated or received TED for tolerabilty evaluation. Two rabbit eyes received no treatment and served as age-matched naive control. The four groups were: Naive (oculus sinister [OS] untreated eyes; n = 9); TED (OS treated only with TED BID for 3 days; n = 9); SM (OD exposed to SM vapor; n = 9); and SM+TED (OD exposed to SM+TED BID for 3 days; n = 9). Ocular examination in live rabbits were performed utilizing slit-lamp biomicroscopy, Fantes grading system, fluorescein staining, Schirmer's tests, pachymetry, and applanation tonometry. Cellular and molecular changes in rabbit corneas were assessed after humane euthanasia on day-3 and day-7 with histopathological and real-time polymerase chain reaction PCR techniques.ResultsTED to rabbit eyes was found tolerable in vivo. SM-exposed eyes showed significant increase in Fantes scores, central corneal thickness (CCT), Schirmer's test, epithelium-stroma separation, and corneal edema. TED mitigated clinical symptoms by reducing corneal edema, Fantes scores, CCT, and Schirmer's test. Further, TED decreased SM-induced corneal haze, inflammatory and profibrotic markers, transforming growth factor–TGF-β1 and cyclooxygenase-2COX-2, and damage to corneal structure, including epithelial-stromal integrity.ConclusionsThe developed multimodal eyedrop formulation, TED, has potential to mitigate acute MGK effectively in vivo.Translational RelevanceTED is effective against MGK

Progressive Lung Injury, Inflammation, and Fibrosis in Rats Following Inhalation of Sulfur Mustard.

Sulfur mustard (SM) inhalation causes debilitating pulmonary injury in humans which progresses to fibrosis. Herein, we developed a rat model of SM toxicity which parallels pathological changes in the respiratory tract observed in humans. SM vapor inhalation caused dose (0.2-0.6 mg/kg)-related damage to the respiratory tract within 3 days of exposure. At 0.4-0.6 mg/kg, ulceration of the proximal bronchioles, edema and inflammation were observed, along with a proteinaceous exudate containing inflammatory cells in alveolar regions. Time course studies revealed that the pathologic response was biphasic. Thus, changes observed at 3 days post-SM were reduced at 7-16 days; this was followed by more robust aberrations at 28 days, including epithelial necrosis and hyperplasia in the distal bronchioles, thickened alveolar walls, enlarged vacuolated macrophages, and interstitial fibrosis. Histopathologic changes were correlated with biphasic increases in bronchoalveolar lavage (BAL) cell and protein content and proliferating cell nuclear antigen expression. Proinflammatory proteins receptor for advanced glycation end product (RAGE), high-mobility group box protein (HMGB)-1, and matrix metalloproteinase (MMP)-9 also increased in a biphasic manner following SM inhalation, along with surfactant protein-D (SP-D). Tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS), inflammatory proteins implicated in mustard lung toxicity, and the proinflammatory/profibrotic protein, galectin (Gal)-3, were upregulated in alveolar macrophages and in bronchiolar regions at 3 and 28 days post-SM. Inflammatory changes in the lung were associated with oxidative stress, as reflected by increased expression of heme oxygenase (HO)-1. These data demonstrate a similar pathologic response to inhaled SM in rats and humans suggesting that this rodent model can be used for mechanistic studies and for the identification of efficacious therapeutics for mitigating toxicity.

Ceramics based on the Sm2O3–Y2O3 and Sm2O3–HfO2 systems at high temperatures: Thermodynamics and modeling

Ceramics based on the Sm2O3–Y2O3 and Sm2O3–HfO2 systems is promising for development of advanced refractory materials including casting molds for gas turbine engine blades and thermal barrier coatings. Vaporization processes and thermodynamic properties of the Sm2O3–Y2O3 and Sm2O3–HfO2 systems were studied by the Knudsen effusion mass spectrometric method. The samples used in the present study were synthesized by the solid-state method. Composition of the vapor over these systems at the temperature 2373 K was the same as over pure oxides. Temperature dependences of the partial pressures of the SmO and Sm vapor species were obtained over pure Sm2O3 in the temperature range 2265–2668 K and over Sm2Hf2O7 in the temperature range 2222–2650 K. The partial pressures of the vapor species, the component activities, and the excess Gibbs energies were determined over a wide concentration ranges in the Sm2O3–Y2O3 and Sm2O3-HfO2 systems at the temperature 2373 K. These thermodynamic functions exhibited negative deviations from the ideality and were compared with the data available for the La2O3–Y2O3, Gd2O3–Y2O3, ZrO2–Y2O3 and La2O3–HfO2, Gd2O3–HfO2, Nd2O3–HfO2 systems. Thermodynamic properties of these binary systems containing yttria and hafnia with rare earth oxides were discussed in the frame of the Generalized Lattice Theory of Associated Solutions. Correlations were found between the observed changes in the thermodynamic behavior of the systems mentioned and the relative number of bonds in the condensed phases when the second coordination sphere was taken into consideration.

Epithelial Repair in the Rabbit Cornea Following Aspects of Epithelial Injury and Repair after Mustard Exposure

Sulfur mustard (SM; bis (2‐chloroethyl) sulfide) is a potent vesicating agent that has been used in chemical warfare. Exposure of the eyes to SM can cause corneal erosions, epithelial defects, neovascularization, microblistering, and/or dry eye disease, all injuries that can lead to corneal epithelium sloughing and ultimately blindness. In the present studies, the effects of ocular exposure to SM vapor (0.420 mg/L for 8 min) on the corneas of male New Zealand white rabbits was characterized at 1, 3, 7, 14, 21 and 28 days post‐exposure. During this time, corneal thickness increased from ~400 microns to 600–900 microns. Unexposed control corneas were clear throughout the time course. However, after SM exposure increased corneal thickness was associated with decreased corneal opacity and neovascularization. Histologically, SM exposure induced epithelial‐stromal separation at 3 days, by which time 16% of the epithelia had separated from the stroma, and by 28 days detachment had decreased to 9%. Also observed was post‐SM epithelial thinning, increased stromal disorganization, and edema. Sporadic keratocytes were also evident in the edematous stroma by day 14. At 28 days post‐SM, an inflammatory cell infiltrate was observed in the stroma. In control corneas, keratin 17, a marker of wound repair, was constitutively expressed in the limbus and bulbar conjunctiva. By 14 days post‐SM, keratin 17 was expressed in the peripheral corneal epithelium, and by 28 days it was expressed in the central cornea. PCNA, a proliferation marker, was constitutively expressed in the nuclei of control corneal epithelial cells. Three days post‐SM, PCNA expression was decreased along the damaged basal layer. Twenty eight days post‐SM, PCNA was upregulated in the nuclei of hyperplastic cells of the central cornea and cells of the limbus, indicating wound repair. These data suggest that limbal and /or conjunctival epithelial cells play a role in the repair of SM‐induced corneal injury. A better understanding of the mechanisms of SM‐induced corneal damage will lead to the development of new therapeutics for the treatment of these debilitating ocular injuries. Supported by NIH grant AR055073.Support or Funding InformationSupported by NIH grant AR055073.

Sulfur Mustard-Induced Ocular Injuries: Update on Mechanisms and Management.

Sulfur mustard (SM; mustard gas) is a classic chemical warfare agent that has been used in several wars and is still a potential threat especially in the Middle-East region. Victims experience acute symptoms in airexposed organs including skin, respiratory tract and the eyes. Survivors of the acute stage might develop chronic or delayed-onset complications in the exposed organs. The exact mechanism(s) of SM-induced tissue damage is still unknown, however DNA alkylation and oxidative damage are the most relevant mechanisms. Eye is the most sensitive organ to the SM vapor and ocular symptoms usually precede other manifestations. Ocular findings including blepharitis, dry eye disease, corneal vascularization, persistent epithelial defects, limbal ischemia, limbal stem cell deficiency, corneal thinning, corneal opacity and corneal innervation abnormalities have been reported several years after SM exposure. In this review, mechanisms of acute and chronic/delayed ocular manifestations of SM and their current management and potential future therapies have been discussed. We have also included recent advances in amniotic membrane transplantation, cultivated stem cell transplantation and anti-angiogenic therapies which might be considered as therapeutic options in SM-induced ocular damage in the future.

Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

Clouds of vaporized samarium (Sm) were released during sounding rocket flights from the Reagan Test Site, Kwajalein Atoll in May 2013 as part of the Metal Oxide Space Cloud (MOSC) experiment. A network of ground-based sensors observed the resulting clouds from five locations in the Republic of the Marshall Islands. Of primary interest was an examination of the extent to which a tailored radio frequency (RF) propagation environment could be generated through artificial ionospheric modification. The MOSC experiment consisted of launches near dusk on two separate evenings each releasing ~6 kg of Sm vapor at altitudes near 170 km and 180 km. Localized plasma clouds were generated through a combination of photoionization and chemi-ionization (Sm + O → SmO+ + e–) processes producing signatures visible in optical sensors, incoherent scatter radar, and in high-frequency (HF) diagnostics. Here we present an overview of the experiment payloads, document the flight characteristics, and describe the experimental measurements conducted throughout the 2 week launch window. Multi-instrument analysis including incoherent scatter observations, HF soundings, RF beacon measurements, and optical data provided the opportunity for a comprehensive characterization of the physical, spectral, and plasma density composition of the artificial plasma clouds as a function of space and time. A series of companion papers submitted along with this experimental overview provide more detail on the individual elements for interested readers.

Structural changes in the skin of hairless mice following exposure to sulfur mustard correlate with inflammation and DNA damage

Sulfur mustard (SM, bis(2-chloroethyl)sulfide) is a bifunctional alkylating agent that causes dermal inflammation, edema and blistering. To investigate the pathogenesis of SM-induced injury, we used a vapor cup model which provides an occlusive environment in which SM is in constant contact with the skin. The dorsal skin of SKH-1 hairless mice was exposed to saturated SM vapor or air control. Histopathological changes, inflammatory markers and DNA damage were analyzed 1–14 days later. After 1 day, SM caused epidermal thinning, stratum corneum shedding, basal cell karyolysis, hemorrhage and macrophage and neutrophil accumulation in the dermis. Cleaved caspase-3 and phosphorylated histone 2A.X (phospho-H2A.X), markers of apoptosis and DNA damage, respectively, were increased whereas proliferating cell nuclear antigen (PCNA) was down-regulated after SM exposure. By 3 days, epithelial cell hypertrophy, edema, parakeratosis and loss of epidermal structures were noted. Enzymes generating pro-inflammatory mediators including myeloperoxidase and cyclooxygenase-2 were upregulated. After 7 days, keratin-10, a differentiation marker, was evident in the stratum corneum. This was associated with an underlying eschar, as neoepidermis began to migrate at the wound edges. Trichrome staining revealed increased collagen deposition in the dermis. PCNA expression in the epidermis was correlated with hyperplasia, hyperkeratosis, and parakeratosis. By 14 days, there was epidermal regeneration with extensive hyperplasia, and reduced expression of cleaved caspase-3, cyclooxygenase-2 and phospho-H2A.X. These findings are consistent with the pathophysiology of SM-induced skin injury in humans suggesting that the hairless mouse can be used to investigate the dermatoxicity of vesicants and the potential efficacy of countermeasures.

Diagnosis of Sulfur Mustard Exposure Based On Epidermal‐Dermal Junction Proteins (Laminin‐5, Integrin) Degradation

Sulfur mustard (SM, 2, 2′-dichlorodiethyl sulfide) is an alkylating vesicant agent. The injuries due to SM are mainly characterized by epithelial damage in exposed tissues such as the skin. In the skin, proteins mostly affected by SM-exposure are laminin-5 and integrin-alpha6beta4. Laminin-5 and integrin-alpha6beta4 constitute the attachment protein complex responsible for epidermal-dermal adhesion. Here, we studied SM specificity, time-course and dose-response for degradation of both laminin-5 and integrin-á6â4 by E-PAGE Western blotting and immunofluorescence staining methods utilizing laminin-5 (beta3 or gamma2 subunit) and integrin-alpha6beta4 antibodies. In the in vitro skin model of cultured normal human epidermal keratinocytes (NHEK), SM degraded both laminin-5 and integrin-á6â4 in a concentration (50–300 ìM)- and time (1–16 hour)-dependent manner. The laminin-5 (gamma2) degradation effect was specific for SM and not for the other alkylating agents tested. Using the Western blotting method, we also validated the SM-induced laminin-5 (gamma2) degradation in vivo in SM vapor cup-exposed hairless guinea pig and mouse skin samples. These results suggest the possibility of utilizing laminin-5 and integrin á6â4 as biomarkers for mustard exposure diagnosis.

Skin toxicokinetics of mustard gas in the guinea pig: effect of hypochlorite and safety aspects.

Sulfur mustard (SM, mustard gas) is a chemical warfare vesicant that rapidly penetrates the skin due to its hydrophobicity. This study measured the rate of SM disappearance from the skin after topical application of the vesicant. In both fur-covered and hairless animals, the remaining toxicant levels measured 60 min after exposure to undiluted SM were 0.6% and 0.3%, respectively, of the initially applied SM amount. However, SM concentration reached 0.4% of the initial dose 3 h following exposure in female fur-covered guinea pigs. SM quantities extracted from skin of male fur-covered and hairless guinea pigs immediately after 16 min of exposure to SM vapor were 12.2 and 21.8 microg, respectively; levels declined to 1.6 and 1.7 microg at 30 and 15 min following termination of exposure of male fur-covered and hairless guinea pigs, respectively. Three swabbing treatments of undiluted SM-exposed skin with gauze pads soaked in 0.5% hypochlorite caused 68% reduction in skin SM content. Similar findings were obtained when hypochlorite was replaced by water (64% reduction). SM content in the gauze pads was 59, 38 and 25 microg, respectively, for the first, second and third decontamination processes with water. No SM was detected in the gauze pads soaked with hypochlorite. In vitro studies showed that incubation of SM with 0.5% hypochlorite at a ratio of 10:1 (v/v) did not cause SM inactivation, whereas 4% hypochlorite reduced SM levels by 17%. However, at a decontaminant:SM ratio of 1000:1, 0.5% and 4% hypochlorite reduced SM levels by 92% and 99%, respectively. These findings are important for health authorities and regulatory agencies in planning precautionary steps to be taken in case of emergency and in routine laboratory work.

Conical emission as a result of self-phase modulation in samarium vapor under the near-resonant condition

We studied the conical emission in samarium (Sm) vapor under the near-resonant condition. The incident dye laser was tuned to the transition line, 4f66s2 7F→4f6(7F)6s6p(1P0)(λ=562.601 nm), of the Sm atom. Using a high-temperature oven, we could obtain the atomic density of 8×1014 atoms/cm3, large enough to observe the conical emission. We observed one to three rings around the original laser beam, and the number of the rings depended on the laser intensity, the laser wavelength, and the atomic density. These results are attributed to the self-phase modulation of the laser beam interacting with the near-resonant atomic medium. We give a simple expression that describes the dependence of the locations of the rings on the laser intensity. We compare the experimental results with this expression quantitatively and then estimate the nonlinear susceptibility of Sm vapor.

Serine and Cysteine Proteases in Sulfur Mustard-Exposed Hairless Mouse Skin: Enzymatic Activity and Inhibition Profiles

AbstractInflammatory reactions associated with sulfur mustard (bis(2-chloroethyl)sulfide, SM)-induced skin pathology, including the release of potent proteolytic enzymes capable of destroying cutaneous connective tissue proteins, are not well defined in vivo. In this study, protease activities were measured as potential indicators of SM-induced skin injury in a hairless mouse sulfur mustard vapor exposure model. We also investigated the effects of synthetic protease inhibitors on SM-induced proteolytic activity. Skin homogenates prepared from hairless mouse dorsal skin exposed to SM vapor (1.4 g/m3) were assayed for serine and cysteine protease activities using synthetic chromogenic and fluorogenic substrates. Skin samples were obtained 24 h after SM challenge from animals exposed for either 6 or 12 min, while controls were obtained from unexposed skin. With 6 min SM-exposed skin, significantly higher elastase, tryptase, cathepsin B, cathepsin L, and calpain II enzymatic activities were detected compared ...

Assessment of cutaneous sulfur mustard injury in the weanling pig

Background/aims:The euthymic hairless guinea pig was the animal model of choice at this laboratory for vesicant injury research. The supply of these animals, however, was interrupted in 1993 by an outbreak of Lisferia monocyfogenes at the commercial supplier's breeding facility, thereby forcing a search for alternative animal models. This report describes the development of a weanling pig model for use in evaluating the severity of skin lesions induced by sulfur mustard [bis(2‐chloroethyl)sulfide; SM] using a variety of bioengineering techniques. These methods include reflectance colorimetry (erythema response), high frequency ultrasound imaging (edema response) and a modified dermal torque meter procedure to test for Nikolsky's sign (damage at the dermal‐epidermal junction). The time course and exposure time‐dependence of SM‐induced lesions for these parameters were characterized in this model and compared with previous results in the haired and hairless guinea pig.Methods:Six male Yorkshire Cross pigs (7–10 kg) were used in this study. The hair on the dorsal surface of each animal was shaved the afternoon prior to SM exposure. Twenty‐four dorsal skin sites on each pig were exposed to saturated SM vapor (1.4 mg/l) using 14‐mm diameter vapor cups for 0 (control), 5, 10, 15, 20, or 25 min, with four sites per exposure level. Control and exposure sites were rotated to prevent site‐specific biases. Lesions were evaluated for erythema (reflectance colorimeter) at 4, 6, 12, 24 and 48 h post‐exposure, and for edema (high frequency ultrasound) at 6, 12, 24, and 48 h post‐exposure. Evaluations for Nikolsky's sign and histopathology were conducted at 48 h post‐exposure.Results:Maximum erythema responses occurred at 24 h postexposure for all SM exposure times (5, 10, 15, 20 and 25 min). The overall maximum response occurred with a 15‐min SM vapor exposure at 24 h post‐exposure. Exposures longer than 15 min did not induce significantly greater erythema at any of the time points examined. The earliest time point at which significant edema was noted was at 12 h for the 15‐ and 25‐min SM vapor groups. Maximum edema occurred at 48 h following a 15‐min exposure. No significant increase in edema was noted at any observation time point with exposures longer than 15 min. Allsites showed a weakening of the dermal‐epidermal junction (positive Nikolsky's sign) 48 h after a 15‐min or longer SM vapor challenge. The histologic severity of the lesions did not significantly worsen as the vapor exposure was increased beyond 15 min. (Following a 15‐min SM exposure, incidences of epidermal necrosis, pustular epidermitis, microblisters and vascular damage had reached 100%, with maximum mean severity scores.) The weanling pig is more resistant to the effects of SM vapor than either the haired or hairless guinea pig, showing a delayed response and requiring a longer exposure time to generate the same (quantitative and qualitative) response in erythema, Nikolsky's sign and microblister formation. SM vapor‐induced edema formation in the weanling pig is not as severe as in the guinea pig models.Conclusions:Erythema, Nikolsky's sign and microblisters all appear to be excellent parameters for evaluating SM vapor‐induced cutaneous damage in the weanling pig. Even though the exposure time‐dependent response of cutaneous exposure to SM vapor in humans more closely parallels those of the haired and hairless guinea pig with respect to dermal‐epidermal separation, weanling pig skin shares many more similarities to human skin and has the potential to be a useful model for antivesicant research. This model should prove valuable in 1) efficacy testing of pretreatments, treatments and topical skin protectants; 2) wound healing studies; 3) evaluationlof skinlwound decontamination systems; and 4) basic vesicant research.

Near-Resonant Effects on Propagation of Frequency-Swept Laser Pulse in Atomic Vapor Laser Isotope Separation.

The propagation characteristics of frequency-swept laser pulse in near-resonant medium were studied by the numerical calculation and the experiment. The characteristics of the frequency-swept laser pulse has been largely modified in comparison with the frequency-fixed laser pulse. These modifications were demonstrated also experimentally for Sm vapor. The results agreed well with the numerically calculated.

Optical field induced circular birefringence due to collision-induced zeeman coherence in Sm vapor

An optical field induced circular birefringence due to collision-induced Zeeman coherence in Sm with He has been observed. The integrated intensity and linewidth of the signal have been measured as a linear function of buffer gas pressure. The cross section for destruction of orientation in the ground state of Sm with He has been obtained.

Collision-induced Ramsey resonances in Sm vapor.

Ramsey’s method of separated fields for the observation of narrow radiofrequency (rf) resonances is well known from atomic and molecular beam experiments /l /. In this contribution, we demonstrate the occurrence of similar Ramsey resonances in an atomic vapor due to collisional velocity diffusion of sublevel coherence within an optical Doppler distribution; here the velocity diffusion of sublevel coherence between the excitation and detection processes plays a role similar to the spatial motion of the active atoms in conventional Ramsey experiments. The new phenomenon is observed using coherent resonance Raman processes to optically induce and detect Zeeman coherence in the Sm λ=570.68 nm J=1 - J’=0 transition.

Collision-Induced Ramsey Resonances in Sm Vapor

Collision-Induced Ramsey Resonances in Sm Vapor

Collision-induced Ramsey resonances in Sm vapor.

We report on the observation of novel Ramsey-type resonances due to collisional velocity diffusion in atomic samarium vapor in the presence of rare-gas perturbers. The experimental technique uses counterpropagating laser fields and relies on coherent resonance Raman processes to optically excite and detect sublevel coherence within the Doppler-broadened $^{154}\mathrm{Sm}$ $\ensuremath{\lambda}=570.68$-nm $^{7}F_{1}\ensuremath{-}^{7}F_{0}$ transition. The experimental findings are in good agreement with theoretical predictions based on a Fokker-Planck equation; time constants for the collisional thermalization of Sm in He and Ne atmospheres are derived from our data.