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PubMedDate not supplied

Effect of head rotation in whiplash-type rear impacts.

BACKGROUND CONTEXT: Knowledge is increasing about the electromyographic and kinematic response of the neck muscles to rear impact, and also recent information is available on the effect of a rear impact offset to the left (posterolateral). The effect of head rotation, however, at the time of rear impact is not known. PURPOSE: The purpose of this study was to examine the effects of head rotation to the left and right on the cervical muscle response to increasing low-velocity posterolateral impacts. STUDY DESIGN/SETTING: Twenty healthy volunteers were subjected to rear impacts of 4.7, 8.3, 10.9 and 13.7 m/s2 acceleration, offset by 45 degrees to the subject's left, with head rotation to right and left. METHODS: Bilateral electromyograms of the sternocleidomastoids, trapezii and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the sled, torso at the shoulder level, and head of the participant. RESULTS: With the head rotated to the right, at an acceleration of 13.7 m/s2, the left sternocleidomastoid generated 59% and the right sternocleidomastoid 20% of their maximal voluntary contraction (MVC) electromyogram (EMG). Under these conditions, the remaining muscles (both splenii capitis and trapezius) generated 25% or less of their MVC. With the head rotated to the left, at an acceleration of 13.7 m/s2, the right sternocleidomastoid generated 65% and the left sternocleidomastoid only 11% of the MVC EMG. Under these conditions, again the remaining muscles had low EMG activity (27% or less) with the exception of the left trapezius which generated 47% of its MVC. Electromyographic variables were significantly affected by the levels of acceleration (p<.01). The time to onset and time to peak EMG for all muscles progressively decreased with increasing levels of acceleration, for both head rotation conditions. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (p<.01). CONCLUSIONS: Direction of impact is a factor in determining the muscle response to whiplash, but head rotation at the time of impact is also important in this regard. More specifically, when a rear impact is left posterolateral, it results in increased EMG generation mainly in the contralateral sternocleidomastoid, as expected, but head rotation at the same time in this type of impact reduces the EMG response of the cervical muscles. Muscle injury seems less likely under these conditions in low-velocity impacts.

Acceleration↗
PubMed1995

Balloon angioplasty versus rotational angioplasty in chronic coronary occlusions (the BAROCCO study).

Chronic total coronary occlusion remains one of the limitations of percutaneous transluminal coronary angioplasty, and few therapeutic devices are specifically designed to address this problem. Among such devices, low-speed rotational angioplasty could improve the primary success rate of the procedure but has never been studied in a controlled trial. One hundred consecutive patients with total coronary occlusion (duration 10 days to 1 year) and an indication for myocardial revascularization were randomized to either rotational or conventional angioplasty if the occlusion morphology was judged suitable for either technique. All baseline variables were evenly distributed among the 2 groups. The primary success rate in the rotational angioplasty groupø was 66% (33 of 50) compared with 52% (26 of 50) in the conventional angioplasty group before crossover to the rotational technique (p=NS). According to lesion morphology, the respective primary success rates were 77% (10 of 13) versus 92% (11 of 12) for tapered occlusions (p=NS), and 61% (22 of 36) versus 38% (14 of 37) for "stump-like" occlusions (p < 0.05). After taking into account the crossovers after failed conventional angioplasty, there was no benefit in performing rotational angioplasty first versus conventional angioplasty first (primary success rates 66% vs 60%, p=NS). Thus, in chronic coronary occlusions of tapered morphology, rotational angioplasty is not superior to conventional angioplasty. In stump-like occlusions, the primary success rate is higher with the rotational angioplasty technique; however ther is a disadvantage in using rotational angioplasty as a second-line device if the conventional technique is unsuccessful.

Aged↗
PubMed1997

Isometric torso rotation strength: effect of training frequency on its development.

OBJECTIVE: To examine training frequency's effect on torso rotation muscle strength. DESIGN: The study followed a pretest-posttest randomized-group design. SETTING: University laboratory. PATIENTS: Subjects, 33 men (age 30 +/- 11yr) and 25 women (age 28 +/- 10yr) with no history of low back pain, volunteered to participate in the study and were tested for isometric (IM) torso rotation strength before (T1) and after (T2) 12 weeks of training. Measurements of maximal voluntary IM torso rotation torque (N.m) were made through a 108 degrees range of motion (54 degrees, 36 degrees, 18 degrees, 0 degree, -18 degrees, -36 degrees, -54 degrees). Subjects were stratified by peak torque at T1, and randomized to a nonexercising control group (C, n = 10), or groups that trained once a week (1x/wk, n = 16), twice a week (2x/wk, n = 17), or three times a week (3x/wk, n = 15); and all groups were similar in strength. INTERVENTIONS: Training consisted of 8 to 12 repetitions of full range dynamic variable resistance exercise to volitional fatigue, for both left and right rotation. MAIN OUTCOME: To determine the best training frequency for the development of torso rotation strength. RESULTS: Relative improvements (average increase in strength gained at each angle) for the training groups were 4.9%, 16.3%, and 11.9% for the 1, 2, and 3x/wk groups, respectively. The 1x/wk group did not increase in IM torso rotation strength compared to the control group at any angle. Both the 2 and 3x/ wk groups increased their IM torso rotation strength compared to the control group at all but one angle. There were no significant differences in IM torso rotation strength between the groups that trained 2 or 3x/wk. During the training period, the 2 and 3x/wk groups increased their dynamic training load significantly more than the 1x/wk group. CONCLUSIONS: Posttraining dynamic strength was not different between training frequencies of 2 and 3x/wk. Therefore, training the rotary torso muscles 2x/wk is recommended.

Adult↗
PubMed1984

Light activates rotations of bacteriorhodopsin in the purple membrane.

To investigate how a photoactivated chromophore drives the proton pump mechanism of bacteriorhodopsin, we have observed how the chromophore rotates during the photocyle. To do this, we examined the dichroism induced in aqueous suspensions of purple membrane fragments by flashes of linearly polarized light. We find that the flash stimulates both the photocycling chromophores and their noncycling neighbors to undergo large (greater than 10 degrees - 20 degrees) rotations within the membrane during the photocycle, and that these two chromophore populations undergo distinctly different sequences of rotations. All these rotations could be eliminated by glutaraldehyde fixation as well as by embedding unfixed fragments in polyacrylamide or agarose gels. Thus, in these immbolizing preparations the chromophore can photocycle without rotating inside a bacteriorhodopsin monomer by more than our detection limit of 2 degrees - 5 degrees. The large rotations we observed in aqueous suspensions of purple membranes were probably due to rotations of entire protein monomers. The process by which a photocycling monomer causes its noncycling neighbors to rotate may help explain the highly cooperative behavior bacteriorhodopsin exhibits when it is aggregated into crystalline arrays of trimers.

Bacteriorhodopsins↗
PubMed1989

Microsecond rotational motion of spin-labeled myosin heads during isometric muscle contraction. Saturation transfer electron paramagnetic resonance.

We have used saturation transfer electron paramagnetic resonance (ST-EPR) to detect the microsecond rotational motions of spin-labeled myosin heads in bundles of skinned muscle fibers, under conditions of rigor, relaxation, and isometric contraction. Experiments were performed on fiber bundles perfused continuously with an ATP-regenerating system. Conditions were identical to those we have used in previous studies of myosin head orientation, except that the fibers were perpendicular to the magnetic field, making the spectra primarily sensitive to rotational motion rather than to the orientational distribution. In rigor, the high intensity of the ST-EPR signal indicates the absence of microsecond rotational motion, showing that heads are all rigidly bound to actin. However, in both relaxation and contraction, considerable microsecond rotational motion is observed, implying that the previously reported orientational disorder under these conditions is dynamic, not static, on the microsecond time scale. The behavior in relaxation is essentially the same as that observed when myosin heads are detached from actin in the absence of ATP (Barnett and Thomas, 1984), corresponding to an effective rotational correlation time of approximately 10 microseconds. Slightly less mobility is observed during contraction. One possible interpretation is that in contraction all heads have the same mobility, corresponding to a correlation time of approximately 25 microseconds. Alternatively, more than one motional population may be present. For example, assuming that the spectrum in contraction is a linear combination of those in relaxation (mobile) and rigor (immobile), we obtained a good fit with a mole fraction of 78-88% of the heads in the mobile state. These results are consistent with previous STEPR studies on contracting myofibrils(Thomas et al., 1980). Thus most myosin heads undergo microsecond rotational motions most of the time during isometric contraction, at least in the probed region of the myosin head.These motions could arise primarily from the free rotations of heads detached from actin. However, if most of these heads are attached to actin during contraction, as suggested by stiffness measurements, this result provides support for the hypothesis that sub-millisecond rotational motions of actin-attached myosin heads play an important role in force generation.

Animals↗
PubMed1999

Mathematical relationships between uterine contractions, cervical dilatation, descent and rotation in spontaneous vertex deliveries.

OBJECTIVE: To determine the mathematical relationships between the strength and duration of the uterine contractions, the descent and rotation of the fetal head and the degree of cervical dilatation in 50 multiparous women with spontaneous vaginal deliveries using a simple device applied to the fetal vertex. METHOD: A simple device for monitoring the progress of labor was applied to the fetal vertex. The device allows the continuous monitoring of descent and rotation of the fetal head. The amount of descent and the degree of rotation were also determined by repeated vaginal examinations as well as the degree of cervical dilatation. The frequency of uterine contractions was also recorded on a partogram. RESULT: A good correlation was found between the amount of descent of the fetal vertex (r = 0.975) and between the degree of rotation of the fetal head (0.83) determined by both methods. Multiple regression analysis was then performed and the degree of cervical dilatation in cm at any given time during the first stage of labor was found to be equal to 2.859 + 0.583 fetal head station in (cm) + 0.1983 internal rotation in degrees -0.0493 (station x internal rotation) + 0.1599 station2 + 0.3622 uterine contractions per 10 min. A nomogram was constructed allowing the calculation of cervical dilatation for a given station of the head, degree of rotation and frequency of uterine contractions. CONCLUSION: There is a defined mathematical relationship between the degree of descent and rotation of the fetal head, the degree of cervical dilatation and the frequency of uterine contractions in multiparous women with vertex presentation. The first three variables can be continuously determined by using the described device. Incorporation of the device into a reusable fetal scalp electrode allows the dual mechanical and electronic monitoring during labor with minimal vaginal examinations.

Cervix Uteri↗
PubMed1998

Sex differences in spontaneous locomotor activity and rotational behavior in meadow voles.

Sex differences in rotational behavior have been most clearly established in laboratory rats with females exhibiting a turning bias. Here, using an automated open-field apparatus, locomotor activity and spontaneous rotational behavior were examined in diurnally crepuscularly active reproductive male and female meadow voles (Microtus pennsylvanicus). Meadow voles, being induced ovulators, permitted analysis of females in constant behavioral estrous. Males displayed significantly greater levels of activity and also significantly greater levels of clockwise but not counterclockwise rotational behavior relative to the females. Rotational behavior was less strongly related to activity levels in female as compared to male voles. In addition, females displayed an overall turning bias. These results contrast with findings from laboratory rats in which females are reported to display greater levels of both locomotor activity and rotational behavior. They are, however, consistent with the rotational bias evident in female rats. The present findings confirm the presence of sex differences in rotational behavior and indicate that factors other than activity levels are involved in the generation and/or expression of these sex differences. Sex differences in anxiety and routine-like behavior (i.e., asymmetry in movement) are discussed as possible factors contributing to these male-female differences in rotational behavior.

Animals↗
PubMed1986

Chloroplast coupling factor 1: dependence of rotational correlation time on polypeptide composition.

Time-resolved fluorescence depolarization measurements were made on chloroplast coupling factor 1 (CF1) labeled with pyrenylmaleimide. Rotational correlation times were determined for native CF1, for CF1 lacking epsilon and/or delta polypeptides, and for activated enzyme. The rotational correlation time measured is characteristic of the rotation of the entire enzyme. Removal of the delta polypeptide resulted in a 25% smaller rotational correlation time, although the delta polypeptide contributes less than 5% of the mass of CF1. Removal of the epsilon polypeptide was without effect. Simultaneous removal of delta and epsilon polypeptides produced a 30% smaller rotational correlation time. Activation of CF1 ATPase by incubation with dithiothreitol reduced the rotational correlation time by 15% relative to that of the latent enzyme. The rotational correlation time of CF1 with delta and epsilon polypeptides removed is essentially that expected for a spherical molecule, whereas the other forms of the enzyme can be approximated as ellipsoids of revolution; the axial ratio of the latent enzyme is estimated from the rotational correlation time and the intrinsic viscosity. These data indicate that the delta polypeptide significantly alters the shape of the enzyme and that a conformational change accompanies dithiothreitol activation of the enzyme.

Calcium-Transporting ATPases↗
PubMed1982

Rotational mobility of an erythrocyte membrane integral protein band 3 in dimyristoylphosphatidylcholine reconstituted vesicles and effect of binding of cytoskeletal peripheral proteins.

Band 3 protein was isolated from human erythrocyte membranes, purified, and reconstituted into a well-defined phospholipid bilayer matrix (dimyristoylphosphatidylcholine). The preparation yielded uniform single-bilayered vesicles of the diameter 40--80 nm. The rotational motion of band 3 was studied by saturation transfer electron spin resonance (ESR) spectroscopy of covalently attached maleimide spin-labels. The rotational mobility changed in response to the host lipid phase transition. The rotational correlation time was in a range from 73 (37 degrees C) to 94 microseconds (26 degrees C) in the fluid phase and from 240 (15 degrees C) to 420 microseconds (5 degrees C) in the solid phase. The motion was analyzed based on the anisotropic rotation of band 3 in the reconstituted vesicles. To obtain information on the rotational diffusion constant around the axis parallel to the membrane normal, we made an attempt to measure the angle between the spin-label magnetic axis and the membrane normal. The result gave 3.9 x 10(4) s-1 at 37 degrees C as a rough estimate for the diffusion constant. This is compatible to anisotropic rotation of a cylinder of radius 3.3 nm in a two-dimensional matrix with inner viscosity 2 P and inner thickness 4 nm. The cytoskeletal peripheral proteins caused a definite increase in the rotational correlation time (from 73 to 180 microseconds at 37 degrees C, for example). The restriction of the rotational mobility was shown to be due to the ankyrin-linked interaction between band 3 and spectrin-actin-band 4.1 proteins in the reconstituted membranes.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2005

Femtosecond fluorescence dynamics of rotation-restricted azobenzenophanes: new evidence on the mechanism of trans --> cis photoisomerization of azobenzene.

The ultrafast relaxation dynamics of two rotation-restricted (azobenzeno-2S-phane and azobenzeno-4S-phane) and one rotation-free (4,4'-dimethylazobenzene) azobenzene derivatives were investigated using femtosecond fluorescence up-conversion on both S(1)(n,pi) and S(2)(pi,pi) excitations. On S(2) excitation, pulse-limited kinetics with a decay coefficient of approximately 100 fs corresponding to ultrafast S(2) --> S(1) relaxation is found to be common for all molecules under investigation regardless of the molecular structure. This indicates that a direct rotational relaxation on the S(2) surface is unfavorable. On S(1) excitation, we observed biphasic fluorescence decay with a femtosecond component attributed to the decay of the Franck-Condon state prepared by excitation and a picosecond component attributed to the deactivation of the relaxed molecule on the S(1) surface. This picosecond component is slowed by at least a factor of 2 for the rotation-restricted 2S-bridged molecule compared to that of the rotation-free molecule; for the even stronger rotation-restricted azobenzeno-4S-phane, the decrease is by a factor of 10. These differences in deactivation suggest that the relaxed states and probably the trajectories for rotation-free and rotation-restricted molecules are different on the S(1) surface, which should be important for the quantum yield of photoisomerization.

Journal Article↗
PubMed1998

Mental and manual rotation.

The relation between mental and manual rotation was investigated in 2 experiments. Experiment 1 compared the response times (RTs) of mental rotation about 4 axes in space with the RTs shown in the same task when participants were allowed to reorient the stimuli by means of rotational hand movements. For the 3 Cartesian axes, RT functions were quantitatively indistinguishable. Experiment 2 investigated interference between mental rotation and 4 kinds of simultaneously executed hand movements that did not reorient the stimuli. Interference was observed only when axes of manual and mental rotation coincided in space. Regardless of the hand used, concordant rotational directions facilitated, whereas discordant directions inhibited, mental rotation. The results suggest that mental object rotation and rotatory object manipulation share a common process that is thought to control he dynamics of both imagined and actually performed object reorientation.

Attention↗
PubMed2002

Visuomotor rotations of varying size and direction compete for a single internal model in motor working memory.

When participants adapt to equal and opposite visuomotor rotations in close temporal proximity, memory of the 1st is not consolidated. The authors investigated whether this retrograde interference depends on the use of equal and opposite rotations. On Day 1, different groups of participants adapted to a -30 degrees rotation followed 5 min later by rotations of +30 degrees, +60 degrees, or -60 degrees. On Day 2, all groups were retested on the -30 degrees rotation. Either retrograde interference (in groups who adapted to rotations of opposite sign on Day 1) or retrograde facilitation (in the remaining group) was observed. In all groups, learning of the 2nd rotation resulted in unlearning of the first, indicating that all visuomotor rotations compete for common working memory resources.

Arm↗
PubMed1980

Emergent two-dimensional patterns in images rotated in depth.

Once a person has observed a three-dimensional scene, how accurately can he or she then imagine the appearance of that scene from different viewing angles? In a series of experiments addressed to this question, subjects formed mental images of a set of objects hanging in a clear cylinder and mentally rotated their images as they physically rotated the cylinder by various amounts. They were asked to perform four tasks, each demanding the ability to "see" the two-dimensional patterns that should emerge in their images if the images depicted the new perspective view accurately--(a) Subjects described the two-dimensional geometric shape that the imagined objects formed in an image rotated 90 degrees; (b) they "scanned" horizontally from one imagined object to another in a rotated image; (c) they physically rotated the empty cylinder together with their image until two of the imagined objects were vertically aligned; and (d) they adjusted a marker to line up with a single object in a rotated image. The experimental results converged to suggest that subjects' images accurately displayed the two-dimensional patterns emerging from a rotation in depth. However, the amount by which they rotated their image differed systematically from the amount specified by the experimenter. Results are discussed in the context of a model of the mental representation of physical space that incorporates two types of structures, one representing the three-dimensional layout of a scene, and the other representing the two-dimensional perspective view of the scene from a given vantage point.

Adult↗
PubMed2004

Isokinetic shoulder rotator muscles in wheelchair athletes.

OBJECTIVES: To assess the influence of wheelchair propulsion and neurological level on isokinetic shoulder rotational strength. SETTING: University of Montpellier, France METHODS: Data were evaluated in three groups of subjects as follows: 12 nonathletes, 15 tennis players and 21 wheelchair athletes. We then compared 12 high paraplegic athletes (HPA) and nine low paraplegic athletes (LPA) within the group of 21 wheelchair athletes: The isokinetic tests were performed in the seated 45 degrees abducted test position in the scapular plane at 60, 180 and 300 degrees s(-1) for both shoulders. Peak torque and mean power values were gathered and, from these values, the internal/external rotation ratios were calculated. RESULTS: Intergroup comparison showed an influence of lesion and sport on peak torque at 180 and 300 degrees s(-1) for the internal rotators and significantly higher values of the internal/external ratios in the wheelchair athlete group. For mean power, we observed significant differences under all test conditions and significant differences for ratio only on the dominant side at 180 degrees s(-1) and on the dominant side at 300 degrees s(-1). Comparison of the two groups of paraplegic athletes showed significantly higher values of peak torque and mean power of the external rotators in the LPA for all test conditions. CONCLUSIONS: Neurological level of lesion does not systematically influence the development of internal rotator muscles; in contrast, the participation of the external rotators appears strongly correlated to neurological level. The comparison of the two sides in the two paraplegic groups showed that in two-thirds of the cases the values of the external rotators were significantly higher than those of the internal rotators on the nondominant side for peak torque and mean power. Ratios on the dominant side were systematically higher than on the nondominant side, with significant differences also noted in two-thirds of the cases. These results raise questions about the influence of neurological level and wheelchair propulsion on the muscular adaptations of the shoulder in wheelchair athletes.

Adaptation, Psychological↗
PubMedDate not supplied

[Mineral analysis of roentgenologically defined calcifications in patients with chronic calcifying tendinitis of the rotator cuff].

AIM: Extracorporeal shockwave application (ESWA) is in clinical use to promote disintegration of symptomatic calcifications of the rotator cuff of the shoulder. However, disintegration of roentgenologically comparable calcifications of the rotator cuff is not always successfull. It is known from urologic stone lithotripsy that the susceptibility for disintegration of stone-like concrements depends on their mineral content. Therefore, in the present investigation the relative contents of calcium and phosphorus in rotator cuff calcifications were determined. METHOD: 39 surgically removed rotator cuff calcifications were analyzed by means of atomic emission spectrometry. RESULTS: The relative content of calcium of the rotator cuff calcifications was found to be 22.3 % +/- 5.7 % (mean +/- SD; 6.8 % - 32.4 %), that of phosphorus as 10.5 % +/- 2.4 % (2.7 % - 14.4 %). The data neither depend on the gender of the patients nor on their age at the time point of surgical removal of the rotator cuff calcifications. CONCLUSION: Roentgenologically comparable calcifications of the rotator cuff demonstrated distinct individual differences concerning the relative contents of calcium and phosphorus. The present results may serve as the first indication that the susceptibility of rotator cuff calcifications for disintegration may depend on their relative contents of calcium and phosphorus.

Adult↗
PubMed2005

Path integral methods for rotating molecules in superfluids.

We present a path integral Monte Carlo (PIMC) methodology for quantum simulation of molecular rotations in superfluid environments such as helium and para-hydrogen that combines the sampling of rotational degrees of freedom for a molecular impurity with multilevel Metropolis sampling of Bose permutation exchanges for the solvating species. We show how the present methodology can be applied to the evaluation of imaginary time rotational correlation functions of the molecular impurity, from which the effective rotational constants can be extracted. The combined rotation/permutation sampling approach allows for the first time explicit assessment of the effect of Bose permutations on molecular rotation dynamics, and the converse, i.e., the effect of molecular rotations on permutation exchanges and local superfluidity. We present detailed studies showing that the effect of Bose permutations in the solvating environment is more significant for the dynamics of heavy than light molecules in helium, and that Bose permutation exchanges are slightly enhanced locally by molecular rotation. Finally, the examples studied here reveal a size dependence of rotational excitations for molecules possessing a strongly anisotropic interaction with helium in 4HeN clusters between N approximately 20 and N approximately 10(3).

Journal Article↗
PubMed2006

Ab initio calculations of nonlinear optical rotation by several small chiral molecules and by uridine stereoisomers.

Expressions for nonlinear optical rotation are presented based on the quantum theory of optical birefringence of Atkins and Barron [Proc. R. Soc. London, Ser. A 304, 303 (1968); 306, 119 (1968)]. As concrete examples, the ordinary and nonlinear optical rotations are calculated with density functional theory (DFT) methodology for some simple single-ring molecules, namely, oxaziridine, diaziridine, and their derivatives, and for two, somewhat more complicated, conformations of uridine. For the single-ring molecules, (1) the angles of the ordinary optical rotation are mostly positive and (2) the contributions of the nonlinear effect to the total optical rotation depend both on the nature of the substituted species and of the host atom located on the ring. For the two conformations of uridine, (1) the signs of nonlinear optical rotation differ even though their ordinary optical rotations have the same sign and (2) whether the molecular structures are geometrically optimized with Hartree-Fock or DFT methodologies has no significant effect on the calculated nonlinear optical rotation when gauge-including atomic orbitals were used, even though the basis sets are small. These studies are expected to be helpful for interpretation of experimental results on nonlinear optical rotation by molecules underway in our research group.

Journal Article↗
PubMed2006

Inelastic scattering from glyoxal: collision kinematics rather than the interaction potential dominates rotational channel selection.

Relative cross sections have been obtained for the rotationally and rovibrationally inelastic scattering of S1 trans-glyoxal (CHO-CHO) in its zero point level with K' = 0 from the target gases H2, D2, and He. Emphasis is placed on using crossed molecular beam conditions that provide several choices of collision kinematics (center-of-mass collision energy, relative velocity, center-of-mass collision momentum) for each collision pair. The cross sections define the state-to-state competition among numerous rotational channels involving destination states with DeltaK' ranging from 1 to >15 for collisions with each target gas and under every kinematic condition. They also resolve a similar rotational competition among rovibrational channels where the torsion nu7' is collisionally excited. The cross section sets also allow the relative overall magnitudes of the two types of scattering to be compared. The primary motivation of these experiments concerns the rotationally inelastic scattering. Earlier studies with rare gases and fixed kinematics demonstrated that the distribution of rotational cross sections is remarkably similar from one collision pair to another. The new data show that the competition among rotational channels actually has a small but distinct dependence on kinematic conditions. Data analysis shows that the dependence is a systematic function of the available collision momentum and entirely unrelated to the identity of the target gases, including the heavier rare gases used in earlier studies. The competition among the rotational energy transfer channels and its kinematic heritage is discussed in the context of a classical hard ellipse model of linear momentum to angular momentum conversion much used with room temperature systems. When adapted to our beam conditions, the resulting account of the rotational scattering is accurate and provides insight into the collisional details.

Journal Article↗